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Methamphetamine
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Methamphetamine[note 1] is a central nervous system (CNS) stimulant that is primarily used as a recreational or performance-enhancing drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder (ADHD).[24] It has also been researched as a potential treatment for traumatic brain injury.[7] Methamphetamine was discovered in 1893 and exists as two enantiomers: levo-methamphetamine and dextro-methamphetamine.[note 2] Methamphetamine properly refers to a specific chemical substance, the racemic free base, which is an equal mixture of levomethamphetamine and dextromethamphetamine in their pure amine forms, but the hydrochloride salt, commonly called crystal meth, is widely used. Methamphetamine is rarely prescribed over concerns involving its potential for misuse as an aphrodisiac and euphoriant, among other concerns, as well as the availability of other drugs with comparable effects and treatment efficacy such as dextroamphetamine and lisdexamfetamine.[24] While pharmaceutical formulations of methamphetamine in the United States are labeled as methamphetamine hydrochloride, they contain dextromethamphetamine as the active ingredient.[24][note 3] Dextromethamphetamine is a stronger CNS stimulant than levomethamphetamine.[24]
Both racemic methamphetamine and dextromethamphetamine are illicitly trafficked and sold owing to their potential for recreational use and ease of manufacture. The highest prevalence of illegal methamphetamine use occurs in parts of Asia and Oceania, and in the United States, where racemic methamphetamine and dextromethamphetamine are classified as Schedule II controlled substances. Levomethamphetamine is available as an over-the-counter (OTC) drug for use as an inhaled nasal decongestant in the United States and is seldom abused.[27][note 4] Internationally, the production, distribution, sale, and possession of methamphetamine is restricted or banned in many countries, owing to its placement in schedule II of the United Nations Convention on Psychotropic Substances treaty. While dextromethamphetamine is a more potent drug, racemic methamphetamine is illicitly produced more often, owing to the relative ease of synthesis and regulatory limits of chemical precursor availability.
The effects of methamphetamine are nearly identical to other substituted amphetamine.[30] In low to moderate and therapeutic doses (5-25mg orally)[26], methamphetamine produces typical SNDRA effects and may elevate mood, increase alertness, concentration, and energy, reduce appetite, and promote weight loss. In overdose or during extended binges, it may induce psychosis, breakdown of skeletal muscle, seizures, and bleeding in the brain. Chronic high-dose use can precipitate unpredictable and rapid mood swings, stimulant psychosis (e.g., paranoia, hallucinations, delirium, and delusions), and aggression. Recreationally, methamphetamine's ability to increase energy has been reported to lift mood and increase sexual desire to such an extent that users are able to engage in sexual activity continuously for several days while binging the drug.[31] Methamphetamine is known to possess a high abuse liability (a high likelihood that extratherapeutic use will lead to compulsive drug use) and high psychological dependence liability (a high likelihood that withdrawal symptoms will occur when methamphetamine use ceases). Discontinuing methamphetamine after heavy use may lead to a post-acute-withdrawal syndrome, which can persist for months beyond the typical withdrawal period. At high doses, like other substituted amphetamine, methamphetamine is neurotoxic to human midbrain dopaminergic neurons and, to a lesser extent, serotonergic neurons.[32][33][30] Methamphetamine neurotoxicity causes adverse changes in brain structure and function, such as reductions in grey matter volume in several brain regions, as well as adverse changes in markers of metabolic integrity.[33]
Methamphetamine belongs to the substituted phenethylamine and substituted amphetamine chemical classes and as a drug acts as a serotonin–norepinephrine–dopamine releasing agent. It is related to the other dimethylphenethylamines as a positional isomer of these compounds, which share the common chemical formula C10H15N.
Uses
[edit]Medical
[edit]
In the United States, methamphetamine hydrochloride, sold under the brand name Desoxyn, is FDA-approved for the treatment of attention deficit hyperactivity disorder (ADHD);[26][34] however, the FDA notes that the limited therapeutic usefulness of methamphetamine should be weighed against the risks associated with its use.[26] To avoid toxicity and risk of side effects, FDA guidelines recommend an initial dose of methamphetamine at doses 5–10 mg/day for ADHD in adults and children over six years of age, and may be increased at weekly intervals of 5 mg, up to 25 mg/day, until optimum clinical response is found; the usual effective dose is around 20–25 mg/day.[24][7][26] Methamphetamine is sometimes prescribed off-label for obesity, narcolepsy, and idiopathic hypersomnia.[24][35][36] In the United States, methamphetamine's levorotary form is available in some over-the-counter (OTC) nasal decongestant products.[24][note 4]
Although the pharmaceutical name "methamphetamine hydrochloride" may suggest a racemic mixture, Desoxyn contains enantiopure dextromethamphetamine, which is a more potent stimulant than both levomethamphetamine and racemic methamphetamine.[24][note 3] This naming convention deviates from the standard practice observed with other stimulants, such as Adderall and dextroamphetamine, where the dextrorotary enantiomer is explicitly identified as an active ingredient in both generic and brand-name pharmaceuticals.[37][38][39]
As methamphetamine is associated with a high potential for misuse, the drug is regulated under the Controlled Substances Act and is listed under Schedule II in the United States.[3] Methamphetamine hydrochloride dispensed in the United States is required to include a boxed warning regarding its potential for recreational misuse and addiction liability.[26]
Desoxyn and Desoxyn Gradumet are both pharmaceutical forms of the drug. The latter is no longer produced and is an extended-release form of the drug, flattening the curve of the effect of the drug while extending it.[40]
Recreational
[edit]Methamphetamine is often used recreationally for its effects as a potent euphoriant and stimulant as well as aphrodisiac qualities.[41]
According to a National Geographic TV documentary on methamphetamine, an entire subculture known as party and play is based around sexual activity and methamphetamine use.[41] Participants in this subculture, which consists almost entirely of homosexual male methamphetamine users, will typically meet up through internet dating sites and have sex.[41] Because of its strong stimulant and aphrodisiac effects and inhibitory effect on ejaculation, with repeated use, these sexual encounters will sometimes occur continuously for several days on end.[41] The crash following the use of methamphetamine in this manner is very often severe, with marked hypersomnia (excessive daytime sleepiness).[41] The party and play subculture is prevalent in major US cities such as San Francisco and New York City.[41][42]
_5_mg_tablets.jpg)
Desoxyn tablets – pharmaceutical methamphetamine hydrochloride
Crystal meth – illicit methamphetamine hydrochloride
Methamphetamine shards on a metal milligram scale tray
Contraindications
[edit]Methamphetamine is contraindicated in individuals with a history of substance use disorder, heart disease, or severe agitation or anxiety, or in individuals currently experiencing arteriosclerosis, glaucoma, hyperthyroidism, or severe hypertension.[26] The FDA states that individuals who have experienced hypersensitivity reactions to other stimulants in the past or are currently taking monoamine oxidase inhibitors should not take methamphetamine.[26] The FDA also advises individuals with bipolar disorder, depression, elevated blood pressure, liver or kidney problems, mania, psychosis, Raynaud's phenomenon, seizures, thyroid problems, tics, or Tourette syndrome to monitor their symptoms while taking methamphetamine.[26] Owing to the potential for stunted growth, the FDA advises monitoring the height and weight of growing children and adolescents during treatment.[26]
Adverse effects
[edit]
Physical
[edit]Cardiovascular
[edit]Methamphetamine is a sympathomimetic drug that causes vasoconstriction and tachycardia. Methamphetamine also promotes abnormal extra heartbeats and irregular heart rhythms, which may be life-threatening. [44]
Other physical effects
[edit]The effects can also include loss of appetite, hyperactivity, dilated pupils, flushed skin, excessive sweating, increased movement, dry mouth and teeth grinding (potentially leading to condition informally known as meth mouth), headache, rapid breathing, high body temperature, diarrhea, constipation, blurred vision, dizziness, twitching, numbness, tremors, dry skin, acne, and pale appearance.[26][45] Long-term meth users may have sores on their skin;[46][47] these may be caused by scratching due to itchiness or the belief that insects are crawling under their skin,[46] and the damage is compounded by poor diet and hygiene.[47] Numerous deaths related to methamphetamine overdoses have been reported.[48][49] Additionally, "[p]ostmortem examinations of human tissues have linked use of the drug to diseases associated with aging, such as coronary atherosclerosis and pulmonary fibrosis",[50] which may be caused "by a considerable rise in the formation of ceramides, pro-inflammatory molecules that can foster cell aging and death."[50]
Dental and oral health ("meth mouth")
[edit]
Methamphetamine users, particularly heavy users, may lose their teeth abnormally quickly, regardless of the route of administration, from a condition informally known as meth mouth.[51] The condition is generally most severe in users who inject the drug, rather than swallow, smoke, or inhale it.[51] According to the American Dental Association, meth mouth "is probably caused by a combination of drug-induced psychological and physiological changes resulting in xerostomia (dry mouth), extended periods of poor oral hygiene, frequent consumption of high-calorie, carbonated beverages and bruxism (teeth grinding and clenching)".[51][52] As dry mouth is also a common side effect of other stimulants, which are not known to contribute severe tooth decay, many researchers suggest that methamphetamine-associated tooth decay is more due to users' other choices. They suggest the side effect has been exaggerated and stylized to create a stereotype of current users as a deterrence for new ones.[34]
Sexually transmitted infection
[edit]Methamphetamine use was found to be related to higher frequencies of unprotected sexual intercourse in both HIV-positive and unknown casual partners, an association more pronounced in HIV-positive participants.[53] These findings suggest that methamphetamine use and engagement in unprotected anal intercourse are co-occurring risk behaviors, behaviors that potentially heighten the risk of HIV transmission among gay and bisexual men.[53] Methamphetamine use allows users of both sexes to engage in prolonged sexual activity, which may cause genital sores and abrasions as well as priapism in men.[26][54] Methamphetamine may also cause sores and abrasions in the mouth via bruxism, increasing the risk of sexually transmitted infection.[26][54]
Besides the sexual transmission of HIV, it may also be transmitted between users who share a common needle.[55] The level of needle sharing among methamphetamine users is similar to that among other drug injection users.[55]
Psychological
[edit]The psychological effects of methamphetamine can include euphoria, dysphoria, changes in libido, alertness, apprehension and concentration, decreased sense of fatigue, insomnia or wakefulness, self-confidence, sociability, irritability, restlessness, grandiosity and repetitive and obsessive behaviors.[26][45][56] Peculiar to methamphetamine and related stimulants is "punding", persistent non-goal-directed repetitive activity.[57] Methamphetamine use also has a high association with anxiety, depression, amphetamine psychosis, suicide, and violent behaviors.[58][59]
Neurotoxicity
[edit]
Methamphetamine is directly neurotoxic to dopaminergic neurons in both lab animals and humans.[32][33] Excitotoxicity, oxidative stress, metabolic compromise, UPS dysfunction, protein nitration, endoplasmic reticulum stress, p53 expression and other processes contributed to this neurotoxicity.[32][63][4] In line with its dopaminergic neurotoxicity, methamphetamine use is associated with a higher risk of Parkinson's disease.[64] In addition to its dopaminergic neurotoxicity, a review of evidence in humans indicated that high-dose methamphetamine use can also be neurotoxic to serotonergic neurons.[33] It has been demonstrated that a high core temperature is correlated with an increase in the neurotoxic effects of methamphetamine.[65] Withdrawal of methamphetamine in dependent persons may lead to post-acute withdrawal which persists months beyond the typical withdrawal period.[4]
Magnetic resonance imaging studies on human methamphetamine users have also found evidence of neurodegeneration, or adverse neuroplastic changes in brain structure and function.[33] In particular, methamphetamine appears to cause hyperintensity and hypertrophy of white matter, marked shrinkage of hippocampi, and reduced gray matter in the cingulate cortex, limbic cortex, and paralimbic cortex in recreational methamphetamine users.[33] Moreover, evidence suggests that adverse changes in the level of biomarkers of metabolic integrity and synthesis occur in recreational users, such as a reduction in N-acetylaspartate and creatine levels and elevated levels of choline and myoinositol.[33]
Methamphetamine has been shown to activate TAAR1 in human astrocytes and generate cAMP as a result.[64] Activation of astrocyte-localized TAAR1 appears to function as a mechanism by which methamphetamine attenuates membrane-bound EAAT2 (SLC1A2) levels and function in these cells.[64]
Methamphetamine binds to and activates both sigma receptor subtypes, σ1 and σ2, with micromolar affinity.[62][66] Sigma receptor activation may promote methamphetamine-induced neurotoxicity by facilitating hyperthermia, increasing dopamine synthesis and release, influencing microglial activation, and modulating apoptotic signaling cascades and the formation of reactive oxygen species.[62][66]
Addiction
[edit]| Addiction and dependence glossary[67][68][69] | |
|---|---|
| |
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Current models of addiction from chronic drug use involve alterations in gene expression in certain parts of the brain, particularly the nucleus accumbens.[77][78] The most important transcription factors[note 5] that produce these alterations are ΔFosB, cAMP response element binding protein (CREB), and nuclear factor kappa B (NFκB).[78] ΔFosB plays a crucial role in the development of drug addictions, since its overexpression in D1-type medium spiny neurons in the nucleus accumbens is necessary and sufficient[note 6] for most of the behavioral and neural adaptations that arise from addiction.[68][78][80] Once ΔFosB is sufficiently overexpressed, it induces an addictive state that becomes increasingly more severe with further increases in ΔFosB expression.[68][80] It has been implicated in addictions to alcohol, cannabinoids, cocaine, methylphenidate, nicotine, opioids, phencyclidine, propofol, and substituted amphetamines, among others.[78][80][81][82][83]
ΔJunD, a transcription factor, and G9a, a histone methyltransferase enzyme, both directly oppose the induction of ΔFosB in the nucleus accumbens (i.e., they oppose increases in its expression).[68][78][84] Sufficiently overexpressing ΔJunD in the nucleus accumbens with viral vectors can completely block many of the neural and behavioral alterations seen in chronic drug use (i.e., the alterations mediated by ΔFosB).[78] ΔFosB also plays an important role in regulating behavioral responses to natural rewards, such as palatable food, sex, and exercise.[78][81][85] Since both natural rewards and addictive drugs induce expression of ΔFosB (i.e., they cause the brain to produce more of it), chronic acquisition of these rewards can result in a similar pathological state of addiction.[78][81] ΔFosB is the most significant factor involved in both amphetamine addiction and amphetamine-induced sex addictions, which are compulsive sexual behaviors that result from excessive sexual activity and amphetamine use.[note 7][81][86] These sex addictions (i.e., drug-induced compulsive sexual behaviors) are associated with a dopamine dysregulation syndrome which occurs in some patients taking dopaminergic drugs, such as amphetamine or methamphetamine.[81][85][86]
Epigenetic factors
[edit]Methamphetamine addiction is persistent for many individuals, with 61% of individuals treated for addiction relapsing within one year.[87] About half of those with methamphetamine addiction continue with use over a ten-year period, while the other half reduce use starting at about one to four years after initial use.[88]
The frequent persistence of addiction suggests that long-lasting changes in gene expression may occur in particular regions of the brain, and may contribute importantly to the addiction phenotype. In 2014, a crucial role was found for epigenetic mechanisms in driving lasting changes in gene expression in the brain.[84]
A review in 2015[89] summarized a number of studies involving chronic methamphetamine use in rodents. Epigenetic alterations were observed in the brain reward pathways, including areas like ventral tegmental area, nucleus accumbens, and dorsal striatum, the hippocampus, and the prefrontal cortex. Chronic methamphetamine use caused gene-specific histone acetylations, deacetylations and methylations. Gene-specific DNA methylations in particular regions of the brain were also observed. The various epigenetic alterations caused downregulations or upregulations of specific genes important in addiction. For instance, chronic methamphetamine use caused methylation of the lysine in position 4 of histone 3 located at the promoters of the c-fos and the C-C chemokine receptor 2 (ccr2) genes, activating those genes in the nucleus accumbens (NAc).[89] c-fos is well known to be important in addiction.[90] The ccr2 gene is also important in addiction, since mutational inactivation of this gene impairs addiction.[89]
In methamphetamine addicted rats, epigenetic regulation through reduced acetylation of histones, in brain striatal neurons, caused reduced transcription of glutamate receptors.[91] Glutamate receptors play an important role in regulating the reinforcing effects of addictive drugs.[92]
Administration of methamphetamine to rodents causes DNA damage in their brain, particularly in the nucleus accumbens region.[93][94] During repair of such DNA damages, persistent chromatin alterations may occur such as in the methylation of DNA or the acetylation or methylation of histones at the sites of repair.[95] These alterations can be epigenetic scars in the chromatin that contribute to the persistent epigenetic changes found in methamphetamine addiction.
Treatment and management
[edit]A 2018 systematic review and network meta-analysis of 50 trials involving 12 different psychosocial interventions for amphetamine, methamphetamine, or cocaine addiction found that combination therapy with both contingency management and community reinforcement approach had the highest efficacy (i.e., abstinence rate) and acceptability (i.e., lowest dropout rate).[96] Other treatment modalities examined in the analysis included monotherapy with contingency management or community reinforcement approach, cognitive behavioral therapy, 12-step programs, non-contingent reward-based therapies, psychodynamic therapy, and other combination therapies involving these.[96]
As of December 2019[update], there is no effective pharmacotherapy for methamphetamine addiction.[97][98][99] A systematic review and meta-analysis from 2019 assessed the efficacy of 17 different pharmacotherapies used in randomized controlled trials (RCTs) for amphetamine and methamphetamine addiction;[98] it found only low-strength evidence that methylphenidate might reduce amphetamine or methamphetamine self-administration.[98] There was low- to moderate-strength evidence of no benefit for most of the other medications used in RCTs, which included antidepressants (bupropion, mirtazapine, sertraline), antipsychotics (aripiprazole), anticonvulsants (topiramate, baclofen, gabapentin), naltrexone, varenicline, citicoline, ondansetron, prometa, riluzole, atomoxetine, dextroamphetamine, and modafinil.[98][100]
Medication-Assisted Treatment (MAT) combines FDA-approved medications with behavioral therapies to address substance use disorders. This approach aims to reduce cravings and withdrawal symptoms, supporting individuals in their recovery process.[101]
Dependence and withdrawal
[edit]Tolerance is expected to develop with regular methamphetamine use and, when used recreationally, this tolerance develops rapidly.[102][103] In dependent users, withdrawal symptoms are positively correlated with the level of drug tolerance.[104] Depression from methamphetamine withdrawal lasts longer and is more severe than that of cocaine withdrawal.[105]
According to the current Cochrane review on drug dependence and withdrawal in recreational users of methamphetamine, "when chronic heavy users abruptly discontinue [methamphetamine] use, many report a time-limited withdrawal syndrome that occurs within 24 hours of their last dose".[104] Withdrawal symptoms in chronic, high-dose users are frequent, occurring in up to 87.6% of cases, and persist for three to four weeks with a marked "crash" phase occurring during the first week.[104] Methamphetamine withdrawal symptoms can include anxiety, drug craving, dysphoric mood, fatigue, increased appetite, increased movement or decreased movement, lack of motivation, sleeplessness or sleepiness, and vivid or lucid dreams.[104]
Methamphetamine that is present in a mother's bloodstream can pass through the placenta to a fetus and be secreted into breast milk.[105] Infants born to methamphetamine-abusing mothers may experience a neonatal withdrawal syndrome, with symptoms involving of abnormal sleep patterns, poor feeding, tremors, and hypertonia.[105] This withdrawal syndrome is relatively mild and only requires medical intervention in approximately 4% of cases.[105]
| Form of neuroplasticity or behavioral plasticity |
Type of reinforcer | Ref. | |||||
|---|---|---|---|---|---|---|---|
| Opiates | Psychostimulants | High fat or sugar food | Sexual intercourse | Physical exercise (aerobic) |
Environmental enrichment | ||
| ΔFosB expression in nucleus accumbens D1-type MSNs |
↑ | ↑ | ↑ | ↑ | ↑ | ↑ | [81] |
| Behavioral plasticity | |||||||
| Escalation of intake | Yes | Yes | Yes | [81] | |||
| Psychostimulant cross-sensitization |
Yes | Not applicable | Yes | Yes | Attenuated | Attenuated | [81] |
| Psychostimulant self-administration |
↑ | ↑ | ↓ | ↓ | ↓ | [81] | |
| Psychostimulant conditioned place preference |
↑ | ↑ | ↓ | ↑ | ↓ | ↑ | [81] |
| Reinstatement of drug-seeking behavior | ↑ | ↑ | ↓ | ↓ | [81] | ||
| Neurochemical plasticity | |||||||
| CREB phosphorylation in the nucleus accumbens |
↓ | ↓ | ↓ | ↓ | ↓ | [81] | |
| Sensitized dopamine response in the nucleus accumbens |
No | Yes | No | Yes | [81] | ||
| Altered striatal dopamine signaling | ↓DRD2, ↑DRD3 | ↑DRD1, ↓DRD2, ↑DRD3 | ↑DRD1, ↓DRD2, ↑DRD3 | ↑DRD2 | ↑DRD2 | [81] | |
| Altered striatal opioid signaling | No change or ↑μ-opioid receptors |
↑μ-opioid receptors ↑κ-opioid receptors |
↑μ-opioid receptors | ↑μ-opioid receptors | No change | No change | [81] |
| Changes in striatal opioid peptides | ↑dynorphin No change: enkephalin |
↑dynorphin | ↓enkephalin | ↑dynorphin | ↑dynorphin | [81] | |
| Mesocorticolimbic synaptic plasticity | |||||||
| Number of dendrites in the nucleus accumbens | ↓ | ↑ | ↑ | [81] | |||
| Dendritic spine density in the nucleus accumbens |
↓ | ↑ | ↑ | [81] | |||
Neonatal
[edit]Unlike other drugs, babies with prenatal exposure to methamphetamine do not show immediate signs of withdrawal. Instead, cognitive and behavioral problems start emerging when the children reach school age.[106]
A prospective cohort study of 330 children showed that at the age of 3, children with methamphetamine exposure showed increased emotional reactivity, as well as more signs of anxiety and depression; and at the age of 5, children showed higher rates of externalizing disorders and attention deficit hyperactivity disorder (ADHD).[107]
Overdose
[edit]Methamphetamine overdose is a diverse term. It frequently refers to the exaggeration of the unusual effects with features such as irritability, agitation, hallucinations and paranoia.[5][26] The cardiovascular effects are typically not noticed in young healthy people. Hypertension and tachycardia are not apparent unless measured. A moderate overdose of methamphetamine may induce symptoms such as: abnormal heart rhythm, confusion, difficult or painful urination, high or low blood pressure, high body temperature, over-active or over-responsive reflexes, muscle aches, severe agitation, rapid breathing, tremor, urinary hesitancy, and an inability to pass urine.[5][45] An extremely large overdose may produce symptoms such as adrenergic storm, methamphetamine psychosis, substantially reduced or no urine output, cardiogenic shock, bleeding in the brain, circulatory collapse, hyperpy rexia (i.e., dangerously high body temperature), pulmonary hypertension, kidney failure, rapid muscle breakdown, serotonin syndrome, and a form of stereotypy ("tweaking").[sources 1] A methamphetamine overdose will likely also result in mild brain damage owing to dopaminergic and serotonergic neurotoxicity.[111][33] Death from methamphetamine poisoning is typically preceded by convulsions and coma.[26]
Psychosis
[edit]Use of methamphetamine can result in a stimulant psychosis which may present with a variety of symptoms (e.g., paranoia, hallucinations, delirium, and delusions).[5][112] A Cochrane Collaboration review on treatment for amphetamine, dextroamphetamine, and methamphetamine use-induced psychosis states that about 5–15% of users fail to recover completely.[112][113] The same review asserts that, based upon at least one trial, antipsychotic medications effectively resolve the symptoms of acute amphetamine psychosis.[112] Amphetamine psychosis may also develop occasionally as a treatment-emergent side effect.[114]
Death from overdose
[edit]The CDC reported that the number of deaths in the United States involving psychostimulants with abuse potential to be 23,837 in 2020 and 32,537 in 2021.[115] This category code (ICD–10 of T43.6) includes primarily methamphetamine but also other stimulants such as amphetamine, and methylphenidate. The mechanism of death in these cases is not reported in these statistics and is difficult to know.[116] Unlike fentanyl which causes respiratory depression, methamphetamine is not a respiratory depressant. Some deaths are as a result of intracranial hemorrhage[117] and some deaths are cardiovascular in nature including flash pulmonary edema[118] and ventricular fibrillation.[119][120]
Emergency treatment
[edit]Acute methamphetamine intoxication is largely managed by treating the symptoms and treatments may initially include administration of activated charcoal and sedation.[5] There is not enough evidence on hemodialysis or peritoneal dialysis in cases of methamphetamine intoxication to determine their usefulness.[26] Forced acid diuresis (e.g., with vitamin C) will increase methamphetamine excretion but is not recommended as it may increase the risk of aggravating acidosis, or cause seizures or rhabdomyolysis.[5] Hypertension presents a risk for intracranial hemorrhage (i.e., bleeding in the brain) and, if severe, is typically treated with intravenous phentolamine or nitroprusside.[5] Blood pressure often drops gradually following sufficient sedation with a benzodiazepine and providing a calming environment.[5]
Antipsychotics such as haloperidol are useful in treating agitation and psychosis from methamphetamine overdose.[121][122] Beta blockers with lipophilic properties and CNS penetration such as metoprolol and labetalol may be useful for treating CNS and cardiovascular toxicity.[123][124] The mixed alpha- and beta-blocker labetalol is especially useful for treatment of concomitant tachycardia and hypertension induced by methamphetamine.[121] The phenomenon of "unopposed alpha stimulation" has not been reported with the use of beta-blockers for treatment of methamphetamine toxicity.[121]
Interactions
[edit]Methamphetamine is metabolized by the liver enzyme CYP2D6, so CYP2D6 inhibitors will prolong the elimination half-life of methamphetamine.[26][125] Methamphetamine also interacts with monoamine oxidase inhibitors (MAOIs), since both MAOIs and methamphetamine increase plasma catecholamines; therefore, concurrent use of both is dangerous.[26] Methamphetamine may decrease the effects of sedatives and depressants and increase the effects of antidepressants and other stimulants as well.[26] Methamphetamine may counteract the effects of antihypertensives and antipsychotics owing to its effects on the cardiovascular system and cognition respectively.[26] The pH of gastrointestinal content and urine affects the absorption and excretion of methamphetamine.[26] Specifically, acidic substances will reduce the absorption of methamphetamine and increase urinary excretion, while alkaline substances do the opposite.[26] Owing to the effect pH has on absorption, proton pump inhibitors, which reduce gastric acid, are known to interact with methamphetamine.[26] Norepinephrine reuptake inhibitors (NRIs) like atomoxetine prevent norepinephrine release induced by amphetamines and have been found to reduce the stimulant, euphoriant, and sympathomimetic effects of dextroamphetamine in humans.[126][127][128] Similarly, norepinephrine–dopamine reuptake inhibitors (NRIs) like methylphenidate and bupropion prevent norepinephrine and dopamine release induced by amphetamines and bupropion has been found to reduce the subjective and sympathomimetic effects of methamphetamine in humans.[129][127][130][131]
Pharmacology
[edit]Pharmacodynamics
[edit]| Compound | NE | DA | 5-HT | Ref | ||
|---|---|---|---|---|---|---|
| Phenethylamine | 10.9 | 39.5 | >10,000 | [132][133][134] | ||
| d-Amphetamine | 6.6–7.2 | 5.8–24.8 | 698–1,765 | [135][136] | ||
| l-Amphetamine | 9.5 | 27.7 | ND | [133][134] | ||
| d-Methamphetamine | 12.3–13.8 | 8.5–24.5 | 736–1,292 | [135][137] | ||
| l-Methamphetamine | 28.5 | 416 | 4,640 | [135] | ||
| d-Ethylamphetamine | 28.8 | 44.1 | 333.0 | [138][139] | ||
| Notes: The smaller the value, the more strongly the drug releases the neurotransmitter. The assays were done in rat brain synaptosomes and human potencies may be different. See also Monoamine releasing agent § Activity profiles for a larger table with more compounds. Refs:[140][141] | ||||||
Methamphetamine has been identified as a potent full agonist of trace amine-associated receptor 1 (TAAR1), a G protein-coupled receptor (GPCR) that regulates brain catecholamine systems.[142][143] Activation of TAAR1 increases cyclic adenosine monophosphate (cAMP) production and either completely inhibits or reverses the transport direction of the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT).[142][144] When methamphetamine binds to TAAR1, it triggers transporter phosphorylation via protein kinase A (PKA) and protein kinase C (PKC) signaling, ultimately resulting in the internalization or reverse function of monoamine transporters.[142][145] Methamphetamine is also known to increase intracellular calcium, an effect which is associated with DAT phosphorylation through a Ca2+/calmodulin-dependent protein kinase (CAMK)-dependent signaling pathway, in turn producing dopamine efflux.[146][147][148] TAAR1 has been shown to reduce the firing rate of neurons through direct activation of G protein-coupled inwardly-rectifying potassium channels.[149][150][151] TAAR1 activation by methamphetamine in astrocytes appears to negatively modulate the membrane expression and function of EAAT2, a type of glutamate transporter.[64]
In addition to its effect on the plasma membrane monoamine transporters, methamphetamine inhibits synaptic vesicle function by inhibiting VMAT2, which prevents monoamine uptake into the vesicles and promotes their release.[152] This results in the outflow of monoamines from synaptic vesicles into the cytosol (intracellular fluid) of the presynaptic neuron, and their subsequent release into the synaptic cleft by the phosphorylated transporters.[153] Other transporters that methamphetamine is known to inhibit are SLC22A3 and SLC22A5.[152] SLC22A3 is an extraneuronal monoamine transporter that is present in astrocytes, and SLC22A5 is a high-affinity carnitine transporter.[143][154]
Methamphetamine is also an agonist of the alpha-2 adrenergic receptors and sigma receptors with a greater affinity for σ1 than σ2, and inhibits monoamine oxidase A (MAO-A) and monoamine oxidase B (MAO-B).[62][143][66] Sigma receptor activation by methamphetamine may facilitate its central nervous system stimulant effects and promote neurotoxicity within the brain.[62][66] Dextromethamphetamine is a stronger psychostimulant, but levomethamphetamine has stronger peripheral effects, a longer half-life, and longer perceived effects among heavy substance users.[155][156][157] At high doses, both enantiomers of methamphetamine can induce similar stereotypy and methamphetamine psychosis,[156] but levomethamphetamine has shorter psychodynamic effects.[157]
Pharmacokinetics
[edit]The bioavailability of methamphetamine is 67% orally, 79% intranasally, 67 to 90% via inhalation (smoking), and 100% intravenously.[4][5][6] Following oral administration, methamphetamine is well-absorbed into the bloodstream, with peak plasma methamphetamine concentrations achieved in approximately 3.13–6.3 hours post ingestion.[158] Methamphetamine is also well absorbed following inhalation and following intranasal administration.[5] Because of the high lipophilicity of methamphetamine due to its methyl group, it can readily move through the blood–brain barrier faster than other stimulants, where it is more resistant to degradation by monoamine oxidase.[5][158][159] The amphetamine metabolite peaks at 10–24 hours.[5] Methamphetamine is excreted by the kidneys, with the rate of excretion into the urine heavily influenced by urinary pH.[26][158] When taken orally, 30–54% of the dose is excreted in urine as methamphetamine and 10–23% as amphetamine.[158] Following IV doses, about 45% is excreted as methamphetamine and 7% as amphetamine.[158] The elimination half-life of methamphetamine varies with a range of 5–30 hours, but it is on average 9 to 12 hours in most studies.[5][4] The elimination half-life of methamphetamine does not vary by route of administration, but is subject to substantial interindividual variability.[4]
CYP2D6, dopamine β-hydroxylase, flavin-containing monooxygenase 3, butyrate-CoA ligase, and glycine N-acyltransferase are the enzymes known to metabolize methamphetamine or its metabolites in humans.[sources 2] The primary metabolites are amphetamine and 4-hydroxymethamphetamine;[158] other minor metabolites include: 4-hydroxyamphetamine, 4-hydroxynorephedrine, 4-hydroxyphenylacetone, benzoic acid, hippuric acid, norephedrine, and phenylacetone, the metabolites of amphetamine.[10][158][160] Among these metabolites, the active sympathomimetics are amphetamine, 4‑hydroxyamphetamine,[166] 4‑hydroxynorephedrine,[167] 4-hydroxymethamphetamine,[158] and norephedrine.[168] Methamphetamine is a CYP2D6 inhibitor.[125]
The main metabolic pathways involve aromatic para-hydroxylation, aliphatic alpha- and beta-hydroxylation, N-oxidation, N-dealkylation, and deamination.[10][158][169] The known metabolic pathways include:
Metabolic pathways of methamphetamine in humans[sources 2]
|
Detection in biological fluids
[edit]Methamphetamine and amphetamine are often measured in urine or blood as part of a drug test for sports, employment, poisoning diagnostics, and forensics.[172][173][174][175] Chiral techniques may be employed to help distinguish the source of the drug to determine whether it was obtained illicitly or legally via prescription or prodrug.[176] Chiral separation is needed to assess the possible contribution of levomethamphetamine, which is an active ingredients in some OTC nasal decongestants,[note 4] toward a positive test result.[176][177][178] Dietary zinc supplements can mask the presence of methamphetamine and other drugs in urine.[179]
Chemistry
[edit]
Shards of pure methamphetamine hydrochloride, also known as crystal meth
Methamphetamine is a chiral compound with two enantiomers, dextromethamphetamine and levomethamphetamine. At room temperature, the free base of methamphetamine is a clear and colorless liquid with an odor characteristic of geranium leaves.[13] It is soluble in diethyl ether and ethanol as well as miscible with chloroform.[13]
In contrast, the methamphetamine hydrochloride salt is odorless with a bitter taste.[13] It has a melting point between 170 and 175 °C (338 and 347 °F) and, at room temperature, occurs as white crystals or a white crystalline powder.[13] The hydrochloride salt is also freely soluble in ethanol and water.[13] The crystal structure of either enantiomer is monoclinic with P21 space group; at 90 K (−183.2 °C; −297.7 °F), it has lattice parameters a = 7.10 Å, b = 7.29 Å, c = 10.81 Å, and β = 97.29°.[180]
Degradation
[edit]A 2011 study into the destruction of methamphetamine using bleach showed that effectiveness is correlated with exposure time and concentration.[181] A year-long study (also from 2011) showed that methamphetamine in soils is a persistent pollutant.[182] In a 2013 study of bioreactors in wastewater, methamphetamine was found to be largely degraded within 30 days under exposure to light.[183]
Synthesis
[edit]Racemic methamphetamine may be prepared starting from phenylacetone by either the Leuckart[184] or reductive amination methods.[185] In the Leuckart reaction, one equivalent of phenylacetone is reacted with two equivalents of N-methylformamide to produce the formyl amide of methamphetamine plus carbon dioxide and methylamine as side products.[185] In this reaction, an iminium cation is formed as an intermediate which is reduced by the second equivalent of N-methylformamide.[185] The intermediate formyl amide is then hydrolyzed under acidic aqueous conditions to yield methamphetamine as the final product.[185] Alternatively, phenylacetone can be reacted with methylamine under reducing conditions to yield methamphetamine.[185]
Methamphetamine synthesis
Method of methamphetamine synthesis of methamphetamine via reductive amination
Methods of methamphetamine synthesis via the Leuckart reaction
History, society, and culture
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Amphetamine, discovered before methamphetamine, was first synthesized in 1887 in Germany by Romanian chemist Lazăr Edeleanu who named it phenylisopropylamine.[188][189] Shortly after, methamphetamine was synthesized from ephedrine in 1893 by Japanese chemist Nagai Nagayoshi.[190] Three decades later, in 1919, methamphetamine hydrochloride was synthesized by pharmacologist Akira Ogata via reduction of ephedrine using red phosphorus and iodine.[191]
From 1938, methamphetamine was marketed on a large scale in Germany as a nonprescription drug under the brand name Pervitin, produced by the Berlin-based Temmler pharmaceutical company.[192][193] It was used by all branches of the combined armed forces of the Third Reich, for its stimulant effects and to induce extended wakefulness.[194][195] Pervitin became colloquially known among the German troops as "Stuka-Tablets" (Stuka-Tabletten) and "Herman-Göring-Pills" (Hermann-Göring-Pillen), as a snide allusion to Göring's widely-known addiction to drugs. However, the side effects, particularly the withdrawal symptoms, were so serious that the army sharply cut back its usage in 1940.[196] By 1941, usage was restricted to a doctor's prescription, and the military tightly controlled its distribution. Soldiers would only receive a couple of tablets at a time, and were discouraged from using them in combat. Historian Łukasz Kamieński says,
A soldier going to battle on Pervitin usually found himself unable to perform effectively for the next day or two. Suffering from a drug hangover and looking more like a zombie than a great warrior, he had to recover from the side effects.
Some soldiers turned violent, committing war crimes against civilians; others attacked their own officers.[196] At the end of the war, it was used as part of a new drug: D-IX.
Obetrol, patented by Obetrol Pharmaceuticals in the 1950s and indicated for treatment of obesity, was one of the first brands of pharmaceutical methamphetamine products.[197] Because of the psychological and stimulant effects of methamphetamine, Obetrol became a popular diet pill in the United States in the 1950s and 1960s.[197] Eventually, as the addictive properties of the drug became known, governments began to strictly regulate the production and distribution of methamphetamine.[189] For example, during the early 1970s in the United States, methamphetamine became a schedule II controlled substance under the Controlled Substances Act.[3] As of January 2013, the Desoxyn trademark had been sold to Italian pharmaceutical company Recordati.[198]
Trafficking
[edit]The Golden Triangle (Southeast Asia), specifically Shan State, Myanmar, is the world's leading producer of methamphetamine as production has shifted to ya ba and crystalline methamphetamine, including for export to the United States and across East and Southeast Asia and the Pacific.[199]
Concerning the accelerating synthetic drug production in the region, the Cantonese Chinese syndicate Sam Gor, also known as The Company, is understood to be the main international crime syndicate responsible for this shift.[200] It is made up of members of five different triads. Sam Gor is primarily involved in drug trafficking, earning at least $8 billion per year.[201] Sam Gor is alleged to control 40% of the Asia-Pacific methamphetamine market, while also trafficking heroin and ketamine. The organization is active in a variety of countries, including Myanmar, Thailand, New Zealand, Australia, Japan, China, and Taiwan. Sam Gor previously produced meth in Southern China and is now believed to manufacture mainly in the Golden Triangle, specifically Shan State, Myanmar, responsible for much of the massive surge of crystal meth in circa 2019.[202] The group is understood to be headed by Tse Chi Lop, a gangster born in Guangzhou, China who also holds a Canadian passport.
Liu Zhaohua was another individual involved in the production and trafficking of methamphetamine until his arrest in 2005.[203] It was estimated over 18 tonnes of methamphetamine were produced under his watch.[203]
Legal status
[edit]The production, distribution, sale, and possession of methamphetamine is restricted or illegal in many jurisdictions.[204][205] In some jurisdictions, it is legally available as a prescription medication. Methamphetamine has been placed in schedule II of the United Nations Convention on Psychotropic Substances treaty, indicating that it has limited medical use.[205]
Research
[edit]Animal models have shown that low-dose methamphetamine improves cognitive and behavioural functioning following TBI (traumatic brain injury).[7] This is in contrast to high, repeated doses which cause neurotoxicity. These models demonstrate that low-dose methamphetamine increases neurogenesis and reduces apoptosis in the dentate gyrus of the hippocampus following TBI.[206] It has also been found that TBI patients testing positive for methamphetamine at the time of emergency department admission have lower rates of mortality.[207]
It has been suggested, based on animal research, that calcitriol, the active metabolite of vitamin D, can provide significant protection against the DA- and 5-HT-depleting effects of neurotoxic doses of methamphetamine.[208] Protection against methamphetamine-induced neurotoxicity has also been observed following administration of ascorbic acid (vitamin C),[209] cobalamin (vitamin B12),[210] and vitamin E.[211]
See also
[edit]- 18-MC – Chemical compound
- Breaking Bad – TV drama series centered on illicit methamphetamine synthesis
- Drug checking – Harm reduction technique
- Faces of Meth – Drug prevention project
- Famprofazone – Non-steroidal anti-inflammatory drug yielding methamphetamine as a major metabolite
- Harm reduction – Public health policies which lessen negative aspects of problematic activities
- Methamphetamine and Native Americans
- Methamphetamine in Australia
- Methamphetamine in Bangladesh – Illegal mix of methamphetamine and caffeine
- Methamphetamine in the Philippines
- Methamphetamine in the United States
- Montana Meth Project – Montana-based organization aiming to reduce meth use among teenagers
- Recreational drug use – Use of drugs with the primary intention to alter the state of consciousness
- Rolling meth lab – A transportable laboratory that is used to illegally produce methamphetamine
- Ya ba – Southeast Asian tablets containing a mixture of methamphetamine and caffeine
Footnotes
[edit]- ^ (Text color) Transcription factors
- ^ Methamphetamine is contracted from N-methylamphetamine. Synonyms and alternate spellings include: N-methylamphetamine, desoxyephedrine, Syndrox, Methedrine, and Desoxyn.[14][15][16] Common slang names for methamphetamine include: meth, speed, crank, and shabu (also sabu and shabu-shabu) in Indonesia and the Philippines,[17][18][19][20] and for the hydrochloride crystal, crystal meth, glass, shards, and ice,[21] Tina,[22] and, in New Zealand, P.[23]
- ^ Enantiomers are molecules that are mirror images of one another; they are structurally identical, but of the opposite orientation.
Levomethamphetamine and dextromethamphetamine are also known as L-methamphetamine, (R)-methamphetamine, or levmetamfetamine (International Nonproprietary Name [INN]) and D-methamphetamine, (S)-methamphetamine, or metamfetamine (INN), respectively.[14][25] - ^ a b The medication package insert for Desoxyn lists the chemical name (S)-N,α-dimethylbenzeneethanamine hydrochloride, which explicitly identifies the compound as dextromethamphetamine (the S-enantiomer) with no stereochemical ambiguity.[26]
- ^ a b c The active ingredient in some OTC inhalers in the United States is listed as levmetamfetamine, the INN and USAN of levomethamphetamine.[28][29]
- ^ Transcription factors are proteins that increase or decrease the expression of specific genes.[79]
- ^ In simpler terms, this necessary and sufficient relationship means that ΔFosB overexpression in the nucleus accumbens and addiction-related behavioral and neural adaptations always occur together and never occur alone.
- ^ The associated research only involved amphetamine, not methamphetamine; however, this statement is included here due to the similarity between the pharmacodynamics and aphrodisiac effects of amphetamine and methamphetamine.
Reference notes
[edit]References
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Methamphetamine, a central nervous system stimulant drug, is p-hydroxylated by CYP2D6 to less active p-OH-methamphetamine.
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METH is a schedule II drug, which can only be prescribed for attention deficit hyperactivity disorder (ADHD), extreme obesity, or narcolepsy (as Desoxyn; Recordati Rare Diseases LLC, Lebanon, NJ), with amphetamine being prescribed more often for these conditions due to amphetamine having lower reinforcing potential than METH (Lile et al., 2013). ...
As discussed earlier, the d-enantiomer has stronger CNS effects but is metabolized more quickly than the l-enantiomer, which is longer lasting due to the slower breakdown. ...
l-METH, a vasoconstrictor, is the active constituent of the Vicks Inhaler decongestant (Procter & Gamble, Cincinnati, OH), an over-the-counter product containing about 50 mg of the drug (Smith et al., 2014). Desoxyn, which is d-METH, is rarely medically prescribed due to its strong reinforcing properties. Therapeutic doses of Desoxyn are 20–25 mg daily, taken every 12 hours, with dosing not exceeding 60 mg/day - ^ "Levomethamphetamine". Pubchem Compound. National Center for Biotechnology Information. Archived from the original on 6 October 2014. Retrieved 27 November 2018.
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Topical nasal decongestants --(i) For products containing levmetamfetamine identified in 341.20(b)(1) when used in an inhalant dosage form. The product delivers in every 800 milliliters of air 0.04 to 0.150 milligrams of levmetamfetamine.
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There are several amphetamines used recreationally, including d-amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine, and 3,4-methylenedioxymethamphetamine. Of these compounds, methamphetamine has generated the greatest amount of concern. Indeed, periodically there are statements in the scientific and popular literature attesting to methamphetamine's greater potency and 'addictive' potential, relative to other amphetamines. Such statements, however, are inconsistent with data collected in humans, which show that d-amphetamine and methamphetamine produce nearly identical physiological and behavioral effects (eg, Martin et al, 1971; Sevak et al, 2009; Kirkpatrick et al, in press a).
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Neuroimaging studies have revealed that METH can indeed cause neurodegenerative changes in the brains of human addicts (Aron and Paulus, 2007; Chang et al., 2007). These abnormalities include persistent decreases in the levels of dopamine transporters (DAT) in the orbitofrontal cortex, dorsolateral prefrontal cortex, and the caudate-putamen (McCann et al., 1998, 2008; Sekine et al., 2003; Volkow et al., 2001a, 2001c). The density of serotonin transporters (5-HTT) is also decreased in the midbrain, caudate, putamen, hypothalamus, thalamus, the orbitofrontal, temporal, and cingulate cortices of METH-dependent individuals (Sekine et al., 2006) ...
Neuropsychological studies have detected deficits in attention, working memory, and decision-making in chronic METH addicts ...
There is compelling evidence that the negative neuropsychiatric consequences of METH abuse are due, at least in part, to drug-induced neuropathological changes in the brains of these METH-exposed individuals ...
Structural magnetic resonance imaging (MRI) studies in METH addicts have revealed substantial morphological changes in their brains. These include loss of gray matter in the cingulate, limbic and paralimbic cortices, significant shrinkage of hippocampi, and hypertrophy of white matter (Thompson et al., 2004). In addition, the brains of METH abusers show evidence of hyperintensities in white matter (Bae et al., 2006; Ernst et al., 2000), decreases in the neuronal marker, N-acetylaspartate (Ernst et al., 2000; Sung et al., 2007), reductions in a marker of metabolic integrity, creatine (Sekine et al., 2002) and increases in a marker of glial activation, myoinositol (Chang et al., 2002; Ernst et al., 2000; Sung et al., 2007; Yen et al., 1994). Elevated choline levels, which are indicative of increased cellular membrane synthesis and turnover are also evident in the frontal gray matter of METH abusers (Ernst et al., 2000; Salo et al., 2007; Taylor et al., 2007). - ^ a b Hart CL, Marvin CB, Silver R, Smith EE (February 2012). "Is cognitive functioning impaired in methamphetamine users? A critical review". Neuropsychopharmacology. 37 (3): 586–608. doi:10.1038/npp.2011.276. PMC 3260986. PMID 22089317.
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Glia (including astrocytes, microglia, and oligodendrocytes), which constitute the majority of cells in the brain, have many of the same receptors as neurons, secrete neurotransmitters and neurotrophic and neuroinflammatory factors, control clearance of neurotransmitters from synaptic clefts, and are intimately involved in synaptic plasticity. Despite their prevalence and spectrum of functions, appreciation of their potential general importance has been elusive since their identification in the mid-1800s, and only relatively recently have they been gaining their due respect. This development of appreciation has been nurtured by the growing awareness that drugs of abuse, including the psychostimulants, affect glial activity, and glial activity, in turn, has been found to modulate the effects of the psychostimulants
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Collectively, these pathological processes contribute to neurotoxicity (e.g., increased BBB permeability, inflammation, neuronal degeneration, cell death) and neuropsychiatric impairments (e.g., cognitive deficits, mood disorders)
Loftis JM, Janowsky A (2014). "Figure 7.1: Neuroimmune mechanisms of methamphetamine-induced CNS toxicity". International Review of Neurobiology. 118: 165–197. doi:10.1016/B978-0-12-801284-0.00007-5. PMC 4418472. PMID 25175865." - ^ a b c d e Kaushal N, Matsumoto RR (March 2011). "Role of sigma receptors in methamphetamine-induced neurotoxicity". Curr Neuropharmacol. 9 (1): 54–57. doi:10.2174/157015911795016930. PMC 3137201. PMID 21886562.
σ Receptors seem to play an important role in many of the effects of METH. They are present in the organs that mediate the actions of METH (e.g. brain, heart, lungs) [5]. In the brain, METH acts primarily on the dopaminergic system to cause acute locomotor stimulant, subchronic sensitized, and neurotoxic effects. σ Receptors are present on dopaminergic neurons and their activation stimulates dopamine synthesis and release [11–13]. σ-2 Receptors modulate DAT and the release of dopamine via protein kinase C (PKC) and Ca2+-calmodulin systems [14].
σ-1 Receptor antisense and antagonists have been shown to block the acute locomotor stimulant effects of METH [4]. Repeated administration or self administration of METH has been shown to upregulate σ-1 receptor protein and mRNA in various brain regions including the substantia nigra, frontal cortex, cerebellum, midbrain, and hippocampus [15, 16]. Additionally, σ receptor antagonists ... prevent the development of behavioral sensitization to METH [17, 18]. ...
σ Receptor agonists have been shown to facilitate dopamine release, through both σ-1 and σ-2 receptors [11–14]. - ^ Carvalho M, Carmo H, Costa VM, Capela JP, Pontes H, Remião F, et al. (August 2012). "Toxicity of amphetamines: an update". Arch. Toxicol. 86 (8): 1167–1231. Bibcode:2012ArTox..86.1167C. doi:10.1007/s00204-012-0815-5. PMID 22392347. S2CID 2873101.
- ^ a b c d • Cisneros IE, Ghorpade A (October 2014). "Methamphetamine and HIV-1-induced neurotoxicity: role of trace amine associated receptor 1 cAMP signaling in astrocytes". Neuropharmacology. 85: 499–507. doi:10.1016/j.neuropharm.2014.06.011. PMC 4315503. PMID 24950453.
TAAR1 overexpression significantly decreased EAAT-2 levels and glutamate clearance ... METH treatment activated TAAR1 leading to intracellular cAMP in human astrocytes and modulated glutamate clearance abilities. Furthermore, molecular alterations in astrocyte TAAR1 levels correspond to changes in astrocyte EAAT-2 levels and function.
• Jing L, Li JX (August 2015). "Trace amine-associated receptor 1: A promising target for the treatment of psychostimulant addiction". Eur. J. Pharmacol. 761: 345–352. doi:10.1016/j.ejphar.2015.06.019. PMC 4532615. PMID 26092759.TAAR1 is largely located in the intracellular compartments both in neurons (Miller, 2011), in glial cells (Cisneros and Ghorpade, 2014) and in peripheral tissues (Grandy, 2007)
- ^ Yuan J, Hatzidimitriou G, Suthar P, Mueller M, McCann U, Ricaurte G (March 2006). "Relationship between temperature, dopaminergic neurotoxicity, and plasma drug concentrations in methamphetamine-treated squirrel monkeys". The Journal of Pharmacology and Experimental Therapeutics. 316 (3): 1210–1218. doi:10.1124/jpet.105.096503. PMID 16293712. S2CID 11909155.
- ^ a b c d Rodvelt KR, Miller DK (September 2010). "Could sigma receptor ligands be a treatment for methamphetamine addiction?". Curr Drug Abuse Rev. 3 (3): 156–162. doi:10.2174/1874473711003030156. PMID 21054260.
- ^ Malenka RC, Nestler EJ, Hyman SE (2009). "Chapter 15: Reinforcement and Addictive Disorders". In Sydor A, Brown RY (eds.). Molecular Neuropharmacology: A Foundation for Clinical Neuroscience (2nd ed.). New York: McGraw-Hill Medical. pp. 364–375. ISBN 9780071481274.
- ^ a b c d Nestler EJ (December 2013). "Cellular basis of memory for addiction". Dialogues in Clinical Neuroscience. 15 (4): 431–443. PMC 3898681. PMID 24459410.
Despite the importance of numerous psychosocial factors, at its core, drug addiction involves a biological process: the ability of repeated exposure to a drug of abuse to induce changes in a vulnerable brain that drive the compulsive seeking and taking of drugs, and loss of control over drug use, that define a state of addiction. ... A large body of literature has demonstrated that such ΔFosB induction in D1-type [nucleus accumbens] neurons increases an animal's sensitivity to drug as well as natural rewards and promotes drug self-administration, presumably through a process of positive reinforcement ... Another ΔFosB target is cFos: as ΔFosB accumulates with repeated drug exposure it represses c-Fos and contributes to the molecular switch whereby ΔFosB is selectively induced in the chronic drug-treated state.41. ... Moreover, there is increasing evidence that, despite a range of genetic risks for addiction across the population, exposure to sufficiently high doses of a drug for long periods of time can transform someone who has relatively lower genetic loading into an addict.
- ^ Volkow ND, Koob GF, McLellan AT (January 2016). "Neurobiologic Advances from the Brain Disease Model of Addiction". New England Journal of Medicine. 374 (4): 363–371. doi:10.1056/NEJMra1511480. PMC 6135257. PMID 26816013.
Substance-use disorder: A diagnostic term in the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) referring to recurrent use of alcohol or other drugs that causes clinically and functionally significant impairment, such as health problems, disability, and failure to meet major responsibilities at work, school, or home. Depending on the level of severity, this disorder is classified as mild, moderate, or severe.
Addiction: A term used to indicate the most severe, chronic stage of substance-use disorder, in which there is a substantial loss of self-control, as indicated by compulsive drug taking despite the desire to stop taking the drug. In the DSM-5, the term addiction is synonymous with the classification of severe substance-use disorder. - ^ a b c Renthal W, Nestler EJ (September 2009). "Chromatin regulation in drug addiction and depression". Dialogues in Clinical Neuroscience. 11 (3): 257–268. doi:10.31887/DCNS.2009.11.3/wrenthal. PMC 2834246. PMID 19877494.
[Psychostimulants] increase cAMP levels in striatum, which activates protein kinase A (PKA) and leads to phosphorylation of its targets. This includes the cAMP response element binding protein (CREB), the phosphorylation of which induces its association with the histone acetyltransferase, CREB binding protein (CBP) to acetylate histones and facilitate gene activation. This is known to occur on many genes including fosB and c-fos in response to psychostimulant exposure. ΔFosB is also upregulated by chronic psychostimulant treatments, and is known to activate certain genes (eg, cdk5) and repress others (eg, c-fos) where it recruits HDAC1 as a corepressor. ... Chronic exposure to psychostimulants increases glutamatergic [signaling] from the prefrontal cortex to the NAc. Glutamatergic signaling elevates Ca2+ levels in NAc postsynaptic elements where it activates CaMK (calcium/calmodulin protein kinases) signaling, which, in addition to phosphorylating CREB, also phosphorylates HDAC5.
Figure 2: Psychostimulant-induced signaling events - ^ Broussard JI (January 2012). "Co-transmission of dopamine and glutamate". The Journal of General Physiology. 139 (1): 93–96. doi:10.1085/jgp.201110659. PMC 3250102. PMID 22200950.
Coincident and convergent input often induces plasticity on a postsynaptic neuron. The NAc integrates processed information about the environment from basolateral amygdala, hippocampus, and prefrontal cortex (PFC), as well as projections from midbrain dopamine neurons. Previous studies have demonstrated how dopamine modulates this integrative process. For example, high frequency stimulation potentiates hippocampal inputs to the NAc while simultaneously depressing PFC synapses (Goto and Grace, 2005). The converse was also shown to be true; stimulation at PFC potentiates PFC–NAc synapses but depresses hippocampal–NAc synapses. In light of the new functional evidence of midbrain dopamine/glutamate co-transmission (references above), new experiments of NAc function will have to test whether midbrain glutamatergic inputs bias or filter either limbic or cortical inputs to guide goal-directed behavior.
- ^ Kanehisa Laboratories (10 October 2014). "Amphetamine – Homo sapiens (human)". KEGG Pathway. Retrieved 31 October 2014.
Most addictive drugs increase extracellular concentrations of dopamine (DA) in nucleus accumbens (NAc) and medial prefrontal cortex (mPFC), projection areas of mesocorticolimbic DA neurons and key components of the "brain reward circuit". Amphetamine achieves this elevation in extracellular levels of DA by promoting efflux from synaptic terminals. ... Chronic exposure to amphetamine induces a unique transcription factor delta FosB, which plays an essential role in long-term adaptive changes in the brain.
- ^ Cadet JL, Brannock C, Jayanthi S, Krasnova IN (2015). "Transcriptional and epigenetic substrates of methamphetamine addiction and withdrawal: evidence from a long-access self-administration model in the rat". Molecular Neurobiology. 51 (2): 696–717 (Figure 1). doi:10.1007/s12035-014-8776-8. PMC 4359351. PMID 24939695.
- ^ a b c Robison AJ, Nestler EJ (November 2011). "Transcriptional and epigenetic mechanisms of addiction". Nature Reviews Neuroscience. 12 (11): 623–637. doi:10.1038/nrn3111. PMC 3272277. PMID 21989194.
ΔFosB serves as one of the master control proteins governing this structural plasticity. ... ΔFosB also represses G9a expression, leading to reduced repressive histone methylation at the cdk5 gene. The net result is gene activation and increased CDK5 expression. ... In contrast, ΔFosB binds to the c-fos gene and recruits several co-repressors, including HDAC1 (histone deacetylase 1) and SIRT 1 (sirtuin 1). ... The net result is c-fos gene repression.
Figure 4: Epigenetic basis of drug regulation of gene expression - ^ a b c Nestler EJ (December 2012). "Transcriptional mechanisms of drug addiction". Clinical Psychopharmacology and Neuroscience. 10 (3): 136–143. doi:10.9758/cpn.2012.10.3.136. PMC 3569166. PMID 23430970.
The 35-37 kD ΔFosB isoforms accumulate with chronic drug exposure due to their extraordinarily long half-lives. ... As a result of its stability, the ΔFosB protein persists in neurons for at least several weeks after cessation of drug exposure. ... ΔFosB overexpression in nucleus accumbens induces NFκB ... In contrast, the ability of ΔFosB to repress the c-Fos gene occurs in concert with the recruitment of a histone deacetylase and presumably several other repressive proteins such as a repressive histone methyltransferase
- ^ Nestler EJ (October 2008). "Transcriptional mechanisms of addiction: Role of ΔFosB". Philosophical Transactions of the Royal Society B: Biological Sciences. 363 (1507): 3245–3255. doi:10.1098/rstb.2008.0067. PMC 2607320. PMID 18640924.
Recent evidence has shown that ΔFosB also represses the c-fos gene that helps create the molecular switch—from the induction of several short-lived Fos family proteins after acute drug exposure to the predominant accumulation of ΔFosB after chronic drug exposure
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ΔFosB has been linked directly to several addiction-related behaviors ... Importantly, genetic or viral overexpression of ΔJunD, a dominant-negative mutant of JunD which antagonizes ΔFosB- and other AP-1-mediated transcriptional activity, in the NAc or OFC blocks these key effects of drug exposure14,22–24. This indicates that ΔFosB is both necessary and sufficient for many of the changes wrought in the brain by chronic drug exposure. ΔFosB is also induced in D1-type NAc MSNs by chronic consumption of several natural rewards, including sucrose, high-fat food, sex, wheel running, where it promotes that consumption14,26–30. This implicates ΔFosB in the regulation of natural rewards under normal conditions and perhaps during pathological addictive-like states.
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ΔFosB is an essential transcription factor implicated in the molecular and behavioral pathways of addiction following repeated drug exposure.
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Similar to environmental enrichment, studies have found that exercise reduces self-administration and relapse to drugs of abuse (Cosgrove et al., 2002; Zlebnik et al., 2010). There is also some evidence that these preclinical findings translate to human populations, as exercise reduces withdrawal symptoms and relapse in abstinent smokers (Daniel et al., 2006; Prochaska et al., 2008), and one drug recovery program has seen success in participants that train for and compete in a marathon as part of the program (Butler, 2005). ... In humans, the role of dopamine signaling in incentive-sensitization processes has recently been highlighted by the observation of a dopamine dysregulation syndrome in some patients taking dopaminergic drugs. This syndrome is characterized by a medication-induced increase in (or compulsive) engagement in non-drug rewards such as gambling, shopping, or sex (Evans et al., 2006; Aiken, 2007; Lader, 2008).
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It has been found that deltaFosB gene in the NAc is critical for reinforcing effects of sexual reward. Pitchers and colleagues (2010) reported that sexual experience was shown to cause DeltaFosB accumulation in several limbic brain regions including the NAc, medial pre-frontal cortex, VTA, caudate, and putamen, but not the medial preoptic nucleus. ... these findings support a critical role for DeltaFosB expression in the NAc in the reinforcing effects of sexual behavior and sexual experience-induced facilitation of sexual performance. ... both drug addiction and sexual addiction represent pathological forms of neuroplasticity along with the emergence of aberrant behaviors involving a cascade of neurochemical changes mainly in the brain's rewarding circuitry.
- ^ a b Pitchers KK, Vialou V, Nestler EJ, Laviolette SR, Lehman MN, Coolen LM (February 2013). "Natural and drug rewards act on common neural plasticity mechanisms with ΔFosB as a key mediator". J. Neurosci. 33 (8): 3434–3442. doi:10.1523/JNEUROSCI.4881-12.2013. PMC 3865508. PMID 23426671.
Drugs of abuse induce neuroplasticity in the natural reward pathway, specifically the nucleus accumbens (NAc), thereby causing development and expression of addictive behavior. ... Together, these findings demonstrate that drugs of abuse and natural reward behaviors act on common molecular and cellular mechanisms of plasticity that control vulnerability to drug addiction, and that this increased vulnerability is mediated by ΔFosB and its downstream transcriptional targets. ... Sexual behavior is highly rewarding (Tenk et al., 2009), and sexual experience causes sensitized drug-related behaviors, including cross-sensitization to amphetamine (Amph)-induced locomotor activity (Bradley and Meisel, 2001; Pitchers et al., 2010a) and enhanced Amph reward (Pitchers et al., 2010a). Moreover, sexual experience induces neural plasticity in the NAc similar to that induced by psychostimulant exposure, including increased dendritic spine density (Meisel and Mullins, 2006; Pitchers et al., 2010a), altered glutamate receptor trafficking, and decreased synaptic strength in prefrontal cortex-responding NAc shell neurons (Pitchers et al., 2012). Finally, periods of abstinence from sexual experience were found to be critical for enhanced Amph reward, NAc spinogenesis (Pitchers et al., 2010a), and glutamate receptor trafficking (Pitchers et al., 2012). These findings suggest that natural and drug reward experiences share common mechanisms of neural plasticity
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About 5–15% of the users who develop an amphetamine psychosis fail to recover completely (Hofmann 1983) ...
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Further reading
[edit]- Hart CL, Marvin CB, Silver R, Smith EE (February 2012). "Is cognitive functioning impaired in methamphetamine users? A critical review". Neuropsychopharmacology. 37 (3): 586–608. doi:10.1038/npp.2011.276. ISSN 0893-133X. PMC 3260986. PMID 22089317.
- Rusyniak DE (August 2011). "Neurologic manifestations of chronic methamphetamine abuse". Neurologic Clinics. 29 (3): 641–655. doi:10.1016/j.ncl.2011.05.004. PMC 3148451. PMID 21803215.
- Szalavitz M (21 November 2011). "Why the Myth of the Meth-Damaged Brain May Hinder Recovery". Time. Archived from the original on 22 September 2024. Retrieved 22 September 2024.
External links
[edit]
Methamphetamine at Wikipedia's sister projects
- Methamphetamine Poison Information Monograph
- Drug Trafficking: Aryan Brotherhood Methamphetamine Operation Dismantled, FBI
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Grokipedia
Methamphetamine
View on Grokipediafrom Grokipedia
Chemistry
Structure and Properties
Methamphetamine, systematically named N-methyl-1-phenylpropan-2-amine, is a synthetic phenethylamine derivative with the molecular formula C10H15N.[1] Its molecular weight is 149.23 g/mol.[1] The core structure features a benzene ring connected to a two-carbon chain bearing a methyl-substituted amino group at the β-position relative to the phenyl, with an additional methyl group on the α-carbon, distinguishing it from amphetamine by the N-methylation. The N-methyl group increases lipophilicity relative to amphetamine, facilitating faster and greater penetration of the blood-brain barrier, which leads to substantially higher extracellular dopamine levels, stronger and longer-lasting effects, and elevated risks of neurotoxicity and addiction; equivalent pharmacological effects are achieved at lower doses.[11][12] Methamphetamine contains a chiral center at the α-carbon atom, yielding two enantiomers: the (2S)-(+)-enantiomer, known as d-methamphetamine, and the (2R)-(-)-enantiomer, known as l-methamphetamine.[13] These stereoisomers share identical connectivity but differ in spatial arrangement, with the d-form exhibiting greater optical rotation and potency in biological systems due to stereoselective interactions, though their basic chemical properties such as solubility and reactivity are largely similar.[14][10] The free base form of methamphetamine is a colorless, volatile oil at room temperature, with a boiling point of approximately 212 °C at standard pressure.[1] It is freely soluble in water, ethanol, and ether, reflecting its amphiphilic nature from the hydrophobic phenyl ring and hydrophilic amine.[1] The hydrochloride salt, prevalent in pharmaceutical and illicit preparations, appears as odorless white crystals or powder, with a melting point of 170–175 °C and enhanced water solubility due to ionic dissociation.[1] As a weak base, methamphetamine has a pKa of 9.87 for its conjugate acid, facilitating protonation in acidic environments and influencing its absorption and distribution.[15]| Property | Value | Form/Notes |
|---|---|---|
| Log P (octanol-water) | 2.15 | Indicates moderate lipophilicity[16] |
| Topological polar surface area | 12.03 Ų | Relevant for membrane permeability[16] |
| Hydrogen bond donors | 1 | From the amine group[16] |
| Rotatable bonds | 3 | Contributes to conformational flexibility[16] |
Synthesis and Precursors
Methamphetamine can be synthesized through several routes, primarily via the reduction of ephedrine or pseudoephedrine, or through reductive amination of phenyl-2-propanone (P2P) with methylamine.[17][18] The ephedrine/pseudoephedrine reduction method, often employing hydriodic acid and red phosphorus, converts the hydroxyl group to a hydrocarbon while preserving the stereochemistry to yield predominantly d-methamphetamine, the more potent enantiomer.[19] This approach was historically prevalent in the United States until restrictions on precursor availability shifted production dynamics around 2005, though it remains common in smaller clandestine operations.[20] In the P2P route, phenyl-2-propanone undergoes reductive amination, typically with methylamine and a reducing agent such as aluminum amalgam or catalytic hydrogenation, producing racemic methamphetamine that requires resolution for the d-isomer.[21][22] This method dominates large-scale production in regions like Mexico and Europe, where P2P derivatives such as APAAN (alpha-phenylacetoacetonitrile) or methyl alpha-phenylacetoacetate serve as pre-precursors to circumvent controls on direct P2P.[23][24] Alternative syntheses include the Leuckart reaction, involving P2P and N-methylformamide, which generates formyl derivatives subsequently hydrolyzed, though it produces more impurities and lower yields compared to reductive methods.[22] Key precursors include ephedrine and pseudoephedrine, naturally derived or semi-synthetically produced from Ephedra plants or via full chemical synthesis; P2P, often synthesized from phenylacetic acid; and methylamine.[17][25] These chemicals are subject to international controls under the UN Convention Against Illicit Traffic in Narcotic Drugs, with domestic regulations like the U.S. Combat Methamphetamine Epidemic Act of 2005 limiting retail sales of ephedrine/pseudoephedrine products to curb diversion.[24][20] Clandestine syntheses frequently yield impure product due to incomplete reactions or side products like aziridines from over-reduction in HI/Red P methods.[22] Legitimate pharmaceutical production, as for Desoxyn, employs controlled reductive processes akin to the P2P method but under GMP standards, though exact proprietary details are not publicly disclosed.[26]Degradation and Impurities
Methamphetamine demonstrates high chemical stability under standard storage conditions, with concentrations in liver specimens remaining largely unchanged over 24 months at low temperatures.[27] In forensic contexts, seized samples exhibit only minor purity losses, such as 1.59% after 12 months and 6.43% after 32 months, attributable to gradual oxidative or hydrolytic processes.[28] Thermal decomposition begins at elevated temperatures (350–650 °C), yielding volatile fragments detectable via infrared spectroscopy, though methamphetamine proves more thermally resilient than cocaine under vacuum pyrolysis.[29] Photodegradation in aqueous media proceeds via sunlight exposure, involving hydroxylation, hydrogenation, and electrophilic substitution, with rates enhanced by nitrate ions, Fe³⁺, and dissolved organic matter but inhibited or dual-effected by bicarbonate.[30][31] Oxidative treatments, such as UV/H₂O₂ advanced oxidation, similarly target the phenyl ring and amine group, leading to mineralization products like CO₂ and NH₄⁺.[31] In alkaline formalin solutions (pH 7–9.5), decomposition accelerates, converting methamphetamine primarily to N-methylmethamphetamine via formaldehyde-mediated reactions, with over 80% transformation after 30 days in 20% formalin at unadjusted pH.[32][33] Illicit synthesis introduces route-specific organic impurities, enabling forensic profiling. Red phosphorus/hydriodic acid reduction of ephedrine or pseudoephedrine generates iodoephedrine, chloroephedrine, and 1,2-dimethyl-3-phenylaziridine via in situ halogenation and aziridine ring closure.[34][35] Leuckart or reductive amination from phenyl-2-propanone yields N-formylmethamphetamine, 1,3-dimethyl-2-phenylnaphthalene, and 1-benzyl-3-methylnaphthalene as byproducts from formamide intermediates or cyclization.[22][36] APAAN-based routes produce methyl 3-(methylamino)-2-phenylbutanoate and related esters from hydrolysis side reactions.[37] Residual precursors like ephedrine (up to detectable trace levels) and inorganic residues (e.g., phosphorus acids, iodides) persist if purification is incomplete, contrasting with pharmaceutical-grade material where impurities are regulated below 0.1% per compendial standards.[38][39]| Synthesis Route | Characteristic Impurities |
|---|---|
| Ephedrine HI/P reduction | Iodoephedrine, 1,2-dimethyl-3-phenylaziridine, chloroephedrine[34][35] |
| Leuckart (P2P/formamide) | N-formylmethamphetamine, 1-benzyl-3-methylnaphthalene[22][36] |
| Reductive amination (P2P) | 1,3-dimethyl-2-phenylnaphthalene, ephedrine residues[22][36] |
| APAAN hydrolysis | Methyl 3-(methylamino)-2-phenylbutanoate[37] |
Pharmacology
Pharmacodynamics
Methamphetamine functions primarily as a potent releaser of monoamine neurotransmitters in the central nervous system, including dopamine, norepinephrine, and to a lesser extent serotonin, by interacting with their respective plasma membrane transporters and vesicular storage mechanisms. It enters presynaptic neurons via the dopamine transporter (DAT), norepinephrine transporter (NET), and serotonin transporter (SERT), where it inhibits reuptake and promotes reverse transport, leading to efflux of these neurotransmitters into the synaptic cleft. Compared to amphetamine, methamphetamine's N-methyl group increases lipophilicity, facilitating faster and greater blood-brain barrier penetration and resulting in substantially higher extracellular dopamine levels and more intense stimulant effects.[11][3][40] This reversal is facilitated by methamphetamine's ability to alter the transporters' conformational states, shifting them from inward-facing to outward-facing orientations.[41] Additionally, methamphetamine disrupts vesicular monoamine transporter 2 (VMAT2) function, displacing dopamine, norepinephrine, and serotonin from synaptic vesicles into the neuronal cytoplasm, thereby increasing the cytosolic pool available for subsequent release via plasma membrane transporters.[42] Methamphetamine also acts as a direct agonist at trace amine-associated receptor 1 (TAAR1), a G protein-coupled receptor localized on monoaminergic neurons, which enhances transporter-mediated efflux and inhibits firing rates in dopamine and norepinephrine neurons, amplifying synaptic neurotransmitter levels.[41][43] The dextro enantiomer of methamphetamine demonstrates markedly higher affinity for DAT and greater dopamine-releasing potency compared to the levo enantiomer, accounting for the enhanced psychoactive effects and abuse liability of the d-form used in illicit preparations.[44] These actions culminate in heightened stimulation of postsynaptic adrenergic, dopaminergic, and serotonergic receptors, mediating the drug's stimulant properties through downstream signaling cascades involving cyclic AMP and protein kinase A pathways.[45]Pharmacokinetics
Methamphetamine is rapidly absorbed following oral administration, with peak plasma concentrations occurring within 3 to 6 hours.[5] Intravenous administration results in immediate peak levels, while intranasal and smoked routes achieve rapid absorption with bioavailabilities of approximately 79% and 90%, respectively.[44][46] The drug is widely distributed throughout the body, readily crossing the blood-brain barrier due to its lipophilicity, with a volume of distribution averaging 3.24 L/kg in the elimination phase.[46] It accumulates in tissues such as the brain, liver, and lungs, where concentrations can exceed plasma levels.[47] Methamphetamine undergoes hepatic metabolism primarily via cytochrome P450 2D6 (CYP2D6) to its major metabolite, amphetamine, with additional minor pathways including N-demethylation and aromatic hydroxylation.[40] Approximately 30-50% of a dose is excreted unchanged in the urine, while the remainder appears as metabolites, with total urinary recovery reaching 70% within 24 hours.[44] Elimination is predominantly renal, with the rate influenced by urinary pH; acidic conditions enhance excretion of unchanged drug by promoting ionization and trapping in the tubules, whereas alkaline urine prolongs half-life.[40] The plasma elimination half-life averages 10 hours, ranging from 9 to 12 hours across routes of administration, though inter-individual variability arises from factors like CYP2D6 polymorphisms.[48][49] Methamphetamine's subjective effects often last 8–24 hours compared to amphetamine's typical 4–6 hours (depending on dose and formulation), attributable to its greater lipophilicity, enhanced blood-brain barrier penetration, and more sustained dopamine release.[44]Detection Methods
Methamphetamine and its primary metabolite, amphetamine, are detected in biological samples such as urine, blood, saliva, and hair using a two-step process involving initial screening followed by confirmatory analysis to ensure accuracy and minimize false positives.[50] Screening typically employs immunoassays like enzyme-linked immunosorbent assay (ELISA) or enzyme-multiplied immunoassay technique (EMIT), which target methamphetamine and amphetamine but can cross-react with structurally similar compounds such as ephedrine or pseudoephedrine.[51] Confirmatory methods rely on chromatographic separation coupled with mass spectrometry, including gas chromatography-mass spectrometry (GC-MS) and liquid chromatography-tandem mass spectrometry (LC-MS/MS), which provide quantitative results with detection limits as low as 1-10 ng/mL in urine and blood, enabling differentiation of methamphetamine from other amphetamines via chiral analysis of enantiomers.[52] [53] Detection windows depend on the sample matrix, dosage, frequency of use, individual metabolism, hydration, and urinary pH, with acidic conditions prolonging excretion.[54] In urine, methamphetamine is detectable for 1-3 days after a single low dose but up to 7 days in chronic heavy users due to accumulation of metabolites.[55] Blood and plasma offer shorter windows of 12-48 hours for acute detection, reflecting recent use, while saliva mirrors blood with detectability up to 1-4 days.[56] Hair testing extends the window to approximately 90 days, incorporating 1.5 inches of hair growth (about 3 months) at 1 cm per month, though external contamination must be ruled out via washing protocols.[57] [58] In pediatric patients, the detection window for methamphetamine is typically 1-3 days in urine (often 2-3 days for environmentally exposed children; shorter for low-level exposure) and up to approximately 90 days in hair (based on the first 3 cm closest to the scalp, assuming ~1 cm/month growth rate). These windows are similar to adults, with hair testing providing sensitivity for chronic or past exposure, including passive environmental exposure common in pediatric cases. Detection can vary based on dose, frequency, metabolism, and specimen collection timing.[59]| Matrix | Typical Detection Window | Key Considerations |
|---|---|---|
| Urine | 1-3 days (single use); up to 7 days (chronic) | Most common; detects metabolites; pH-sensitive |
| Blood | 12-48 hours | Indicates recent intoxication; requires prompt sampling |
| Saliva | 1-4 days | Non-invasive; correlates with blood levels |
| Hair | Up to 90 days | Retrospective; segment analysis for timeline |
Therapeutic Applications
Approved Medical Uses
Methamphetamine hydrochloride, available as the prescription medication Desoxyn in 5 mg oral tablets, is approved by the United States Food and Drug Administration (FDA) for two primary indications.[61] It is used as part of a comprehensive treatment program for attention deficit hyperactivity disorder (ADHD) in patients aged 6 years and older, where other treatments have proven inadequate.[61][62] The medication functions as a central nervous system stimulant, aiding in symptom management through enhanced neurotransmitter activity.[6] Additionally, Desoxyn is indicated as a short-term adjunct to caloric restriction in a weight reduction regimen for exogenous obesity, specifically for patients with an initial body mass index of 30 kg/m² or greater, or 27 kg/m² or greater in the presence of other risk factors such as hypertension, diabetes, or dyslipidemia.[61] Prolonged administration for obesity is cautioned against due to the risk of drug dependence, with treatment typically limited to a few weeks to avoid tolerance and psychological reliance.[5] Dosage adjustments are made based on clinical response, starting at 5 mg once or twice daily, with careful monitoring for cardiovascular and psychiatric effects.[61][62] Due to its high potential for abuse and severe adverse effects, methamphetamine is classified as a Schedule II controlled substance under the Controlled Substances Act, and its medical use is restricted to supervised settings with periodic reevaluation.[8][61] Prescriptions are rarely issued outside of cases refractory to alternative therapies like methylphenidate or amphetamine salts.[3]Evidence of Efficacy
Methamphetamine hydrochloride, marketed as Desoxyn, has established efficacy for attention-deficit hyperactivity disorder (ADHD) based on clinical evaluations supporting its FDA approval for patients aged 6 years and older.[61] Short-term placebo-controlled studies demonstrate reductions in core ADHD symptoms, including inattention, hyperactivity, and impulsivity, with typical effective doses ranging from 20-25 mg daily in divided administrations.[62] A double-blind comparative trial with lisdexamfetamine (Vyvanse) confirmed Desoxyn's symptom improvement comparable to other amphetamines, though direct head-to-head data remain limited due to its restricted clinical use amid abuse concerns.[63] For exogenous obesity, efficacy evidence derives primarily from mid-20th-century trials, where methamphetamine facilitated short-term weight loss as an adjunct to caloric restriction and exercise.[64] A 1966 study of 78 pediatric patients aged 5-18 reported significant weight reduction over three months, with greater initial losses tapering thereafter, aligning with FDA indications for brief therapy durations to minimize tolerance and dependence risks.[64][65] Modern endorsements are cautious, emphasizing that while appetite suppression via central nervous system stimulation yields measurable reductions—often 1-2 kg weekly initially—sustained benefits are unproven, and regulatory labels restrict use to a few weeks.[6] Overall, therapeutic efficacy rests on amphetamine-class mechanisms enhancing dopamine and norepinephrine signaling, corroborated by empirical symptom scores in ADHD cohorts, yet long-term controlled data are sparse, reflecting post-approval shifts prioritizing lower-potency alternatives.[66] Academic sources, potentially influenced by institutional biases against Schedule II stimulants, underemphasize methamphetamine's potency relative to analogs like dextroamphetamine, despite equivalent or superior short-term outcomes in select trials.[66]Comparisons with Analogues
Methamphetamine, as the N-methylated analogue of amphetamine, demonstrates higher potency in releasing dopamine via reversal of the dopamine transporter, leading to more intense euphoric and stimulant effects compared to amphetamine, primarily due to its greater lipophilicity and faster blood-brain barrier penetration.[12] In therapeutic applications for attention-deficit/hyperactivity disorder (ADHD), dextroamphetamine and mixed amphetamine salts (e.g., Adderall) are preferred over methamphetamine (e.g., Desoxyn) because the latter exhibits elevated abuse potential, as shown by increased self-administration rates in intranasal administration studies modeling recreational routes.[11] Both compounds elevate synaptic dopamine and norepinephrine levels to enhance focus and impulse control, but methamphetamine's pharmacokinetic profile results in a more rapid onset and prolonged duration, potentially offering superior short-term cognitive enhancement in some users while heightening risks of dependence.[67][68] Relative to methylphenidate, a non-amphetamine stimulant used for ADHD that primarily blocks dopamine reuptake rather than promoting release, methamphetamine produces comparable therapeutic benefits in attention and executive function but with greater hyperthermic and neurotoxic potential during equivalent dosing, as observed in rodent models assessing body temperature and striatal damage.[69] User-reported efficacy for methamphetamine in ADHD management rates highly at 8.9 out of 10, exceeding dextroamphetamine's 8.0 rating based on aggregated patient reviews, though clinical guidelines limit methamphetamine prescriptions due to its documented higher reinforcing effects and diversion risks.[70] In contrast to MDMA, another phenethylamine analogue, methamphetamine lacks significant serotonergic activity and instead prioritizes dopaminergic reinforcement, yielding sustained vigilance without MDMA's prosocial or entactogenic effects but with amplified motor activation and reduced acute "negative" mood alterations.[71] For obesity treatment, where methamphetamine was historically approved alongside amphetamine, the analogue's superior appetite suppression correlates with its enhanced monoamine release, yet modern practice favors less potent options like phentermine due to methamphetamine's association with severe withdrawal and cardiovascular strain upon chronic use.[72] Preclinical data indicate that methamphetamine and amphetamine induce similar degrees of hyperthermia and dopaminergic neurotoxicity at high doses, underscoring shared pathophysiological risks that temper their therapeutic utility despite equivalent efficacy in symptom alleviation.[69] Overall, while methamphetamine outperforms certain analogues in potency and subjective reinforcement, its profile necessitates stringent medical oversight to mitigate diversion, contrasting with the broader tolerability of dextroamphetamine formulations.[11]Patterns of Non-Medical Use
Recreational Administration and Effects
Recreational use of methamphetamine predominantly involves non-oral routes to achieve rapid onset of psychoactive effects, with smoking, intranasal insufflation, and intravenous injection being the most common methods.[73] Crystal methamphetamine (slangily known as "Tina" or "crystal Tina", particularly in LGBTQ+ communities and chemsex contexts), appearing as bluish-white shards, is typically smoked by heating it in a pipe or on foil, allowing vapor inhalation into the lungs for quick absorption into the bloodstream.[7][74] Powdered forms are snorted through the nose, where the drug is absorbed via nasal mucosa, or dissolved and injected directly into veins.[73] Oral ingestion occurs less frequently in recreational contexts due to slower onset but involves swallowing powder or tablets.[8] The route of administration significantly influences onset and intensity of effects. Intravenous injection and smoking produce an immediate "rush" within seconds, lasting 8-24 hours depending on dose, driven by rapid brain delivery of the drug.[73] Snorting yields effects in 3-5 minutes with a less intense initial high but similar duration, while oral administration delays onset to 15-60 minutes.[3] These rapid routes heighten addiction risk by reinforcing use through swift reward.[7] Users seek methamphetamine for its potent stimulant properties, including acute euphoria from a rush described by users as "electric" and explosive, with feelings of invincibility, hyper-euphoria, enhanced perceptions like everything in HD, and sensations amplified to an orgasmic level, alongside heightened alertness, increased energy, and elevated mood, often described as a profound sense of confidence and pleasure.[7][75] Additional subjective effects encompass reduced fatigue, enhanced focus, talkativeness, and appetite suppression, facilitating prolonged wakefulness and activity.[76] Hypersexuality and perceived sociability are also reported, contributing to its appeal in social or performance contexts.[3] These effects stem from methamphetamine's release of dopamine, norepinephrine, and serotonin in the brain, amplifying reward pathways beyond natural levels.[7] However, even initial recreational doses can precipitate anxiety, insomnia, or paranoia in sensitive individuals.[73]Uncommon Routes of Administration
While methamphetamine is most commonly administered via smoking (especially crystal form), insufflation (snorting powder), intravenous injection, or oral ingestion, rare instances of intravaginal administration have been documented, either as an intentional route for rapid absorption or incidentally during body stuffing for drug concealment. The vaginal mucosa is highly vascular and absorbent, allowing quick systemic uptake of methamphetamine, which can produce a fast-onset stimulant effect. However, this route is inefficient and highly dangerous. Direct contact with crystalline methamphetamine or undissolved powder often causes significant local irritation, including chemical burns, intense burning pain, inflammation, and potential micro-tears or abrasions to the delicate vaginal tissues due to its caustic nature. Rapid and unpredictable absorption increases the risk of acute overdose, with symptoms such as tachycardia, hypertension, seizures, hyperthermia, and altered mental status. Infections are also heightened due to tissue damage compromising the mucosal barrier. Medical literature reports severe outcomes from intravaginal body stuffing of methamphetamine. In a 2004 case, a 20-year-old woman in custody developed multiple seizures, altered mental status, tachycardia, and hypertension shortly after admitting to concealing plastic-wrapped methamphetamine in her vagina, leading to severe toxicity from leakage and absorption.[77] In a 2014 case, a 23-year-old woman died from methamphetamine toxicity after unintended intravaginal absorption of the drug concealed in her vagina, with autopsy revealing extremely high concentrations in blood, vitreous fluid, and urine.[78] These cases highlight the potential for life-threatening poisoning via this route, far outweighing any perceived benefits compared to standard administration methods.Prevalence and Demographics
In the United States, past-year non-medical methamphetamine use among individuals aged 12 and older stood at 0.9%, affecting approximately 2.6 million people in 2023, according to data from the National Survey on Drug Use and Health (NSDUH) conducted by the Substance Abuse and Mental Health Services Administration (SAMHSA).[79] This represents a continuation of upward trends observed in prior years, with past-year use rising 43% from 1.4 million people in 2015 to 2 million in 2019, driven in part by increased availability from Mexican cartels and shifts toward non-injection routes among diverse user groups including heterosexual men and women as well as sexual minorities.[80] Prevalence was highest in the Western region at 1.1% in 2019, with rural and Midwestern areas showing accelerated growth in use and related overdoses since the mid-2010s.[80] Demographically, methamphetamine use in the US skews toward males, who reported higher past-year rates than females (approximately 1.2% versus 0.6% in recent surveys), though females exhibit higher initiation rates at younger ages and increasing treatment admissions.[81] Age-wise, use peaks among adults aged 26-34, followed closely by those 18-25, with rates declining sharply among adolescents (0.2% for ages 12-17 in 2023) and older adults.[79] By race and ethnicity, non-Hispanic whites and American Indian/Alaska Natives show the highest prevalence, with overdose death rates—serving as a proxy for heavy use patterns—elevated among these groups at 7.5 and 18.4 per 100,000 respectively in recent years, compared to lower rates among non-Hispanic Blacks and Asians.[82] Use is also disproportionately reported among lower socioeconomic strata, including those in poverty or with unstable housing, correlating with economic distress in deindustrialized regions.[80] Globally, methamphetamine accounts for the largest share of amphetamine-type stimulant (ATS) use, with approximately 31 million people using ATS in 2023, predominantly methamphetamine in regions like East and Southeast Asia, North America, and parts of Oceania.[83] The United Nations Office on Drugs and Crime (UNODC) estimates methamphetamine prevalence at around 0.6% of the global adult population, with highest rates in countries such as the Philippines (up to 2.5% in some surveys) and Myanmar, fueled by large-scale production in the Golden Triangle.[84] Demographic patterns mirror US trends in gender imbalance, with males comprising over 75% of users worldwide, though rising female involvement is noted in treatment data from Asia; age concentrations fall in the 20-39 range, often linked to labor-intensive economies and urban migration.[85] These figures, derived from household surveys and seizure data, underscore methamphetamine's dominance over other ATS like amphetamine, with trafficking volumes exceeding those of cocaine in recent years.[86]Subjective and Performance-Enhancing Claims
Recreational users of methamphetamine frequently report subjective experiences of intense euphoria, heightened alertness, increased energy, and reduced need for sleep, which contribute to its appeal for non-medical use.[7] These effects are attributed to the drug's rapid elevation of dopamine levels in the brain's reward pathways, leading to sensations of confidence, disinhibition, and enhanced sociability during acute intoxication.[87] Studies examining self-reported experiences confirm that users perceive methamphetamine as providing a prolonged "high" lasting several hours, often described as superior to that of other stimulants due to its potency and duration.[88] Performance-enhancing claims center on methamphetamine's potential to boost cognitive and physical capabilities in non-medical contexts, such as prolonged work sessions or athletic endeavors. Acutely, methamphetamine has been shown to improve selective cognitive domains, including visuospatial processing and attention, particularly in individuals with baseline deficits, though effects vary by dose and user profile.[89] In experimental effort-based tasks, low doses increase willingness to engage in high-effort activities for greater rewards, independent of mood alterations, suggesting a direct motivational enhancement rather than mere subjective pleasure.[88] [90] For physical performance, related amphetamines extend exercise duration by delaying perceived fatigue, with methamphetamine exhibiting similar mechanisms through central nervous system stimulation, though direct human trials are limited due to ethical constraints.[91] These claims are often invoked by users to justify non-medical use for productivity or competition, yet empirical evidence indicates acute benefits are transient and overshadowed by risks of tolerance and neurotoxicity with repeated exposure.[92] Longitudinal data reveal no sustained performance gains, with chronic users exhibiting deficits in executive function and decision-making that contradict enhancement narratives.[93] Attribution of superior outcomes to methamphetamine in anecdotal reports may stem from placebo-like expectancy effects or selection bias among low performers who experience relative improvements.[94]Risks and Pathophysiology
Acute Physiological Effects
Methamphetamine exerts its acute physiological effects primarily by enhancing the release and inhibiting the reuptake of monoamine neurotransmitters, including dopamine, norepinephrine, and serotonin, via reversal of their transporters and interaction with trace amine-associated receptor 1 (TAAR1).[3] This sympathomimetic action leads to widespread stimulation of the central and peripheral nervous systems, manifesting within minutes of administration depending on the route—rapidly via intravenous or inhalation, more gradually via oral intake.[3] Cardiovascular effects include dose-dependent tachycardia and hypertension, driven by norepinephrine-mediated vasoconstriction and increased cardiac output.[3] [95] Heart rates can elevate significantly, with experimental data in rodents showing increases proportional to doses from 0.1 to 5 mg/kg, alongside potential arrhythmias and vasospasm that risk myocardial ischemia.[95] Mean arterial pressure typically rises acutely, though higher doses may paradoxically depress it in some models due to reflex mechanisms.[95] Central nervous system stimulation produces heightened alertness, euphoria, and motor activity, alongside reduced fatigue and appetite suppression, lasting 6-12 hours.[3] At higher doses, this escalates to agitation, mydriasis, and hyperreflexia, with risks of seizures from excessive dopaminergic and noradrenergic surge.[3] Thermoregulatory disruption causes hyperthermia, often exceeding 2-4°C elevation via non-shivering thermogenesis in brown adipose tissue and impaired heat dissipation from vasoconstriction.[95] This is exacerbated by environmental factors or exertion, correlating with elevated heart rate and respiratory drive.[95] Respiratory effects involve increased ventilatory frequency and inspiratory drive, independent of CO2 levels, potentially leading to tachypnea.[95] Other acute manifestations include diaphoresis, bruxism, and gastrointestinal symptoms like nausea, all stemming from autonomic overactivation.[3] These effects underscore methamphetamine's potency as a CNS stimulant, with rapid onset tied to its pharmacokinetics—peak plasma levels in 1-3 hours orally, faster via other routes.[3] Paradoxical vaginal lubricationSome female users report paradoxical increased vaginal lubrication shortly after methamphetamine use (particularly intravenous), accompanied by a flushing sensation. Animal studies (e.g., in rats) demonstrate dose-dependent increases in vaginal lubrication mediated by nitric oxide pathways and potentially hormonal changes. This contrasts with methamphetamine's general drying effect on other mucous membranes (such as xerostomia) and may relate to enhanced sexual arousal or vasocongestion, though direct intravaginal insertion typically causes irritation overriding this effect.
Chronic Physical Harm
Chronic methamphetamine use induces widespread physical deterioration across multiple organ systems, primarily through sustained sympathetic overstimulation, vasoconstriction, oxidative stress, and neglect of self-care.[7] Users exhibit accelerated aging-like symptoms, including profound weight loss and muscle wasting due to appetite suppression and hypermetabolic states, often compounded by malnutrition from irregular eating habits. Methamphetamine use significantly shortens lifespan, particularly in elderly individuals, by accelerating biological aging, including shorter telomeres leading to premature cellular senescence, and increasing risks of cardiovascular diseases, neurological complications, chronic conditions such as diabetes and depression, overdose, and overall higher mortality compared to the general population. Chronic use often results in premature death, with studies showing elevated deaths in midlife and older adults (50-75 years) from methamphetamine-related poisoning and complications.[96][97][3] While risks are markedly lower with very infrequent low-dose use compared to chronic patterns, repeated exposures—even annually—may contribute to subtle cumulative endothelial damage, oxidative stress, and vascular alterations over years, potentially elevating long-term cardiovascular risks (e.g., accelerated atherosclerosis, cardiomyopathy). The drug's strong reinforcing properties pose a significant risk of behavioral escalation or dependence even from sporadic use, as tolerance can develop rapidly and cravings may undermine intended limits. Cardiovascular pathology represents a primary chronic harm, with methamphetamine promoting endothelial dysfunction, hypertension, and structural heart remodeling. Long-term exposure elevates risks of cardiomyopathy, myocardial infarction, and heart failure, with studies indicating methamphetamine-associated cardiomyopathy admissions rose significantly in regions of high prevalence, such as California, where it rivals alcohol-related damage in severity.[98] [99] Autopsy data and clinical cohorts reveal dilated cardiomyopathy with fibrosis and reduced ejection fractions in chronic users, attributable to catecholamine excess and direct myocardial toxicity.[100] Pulmonary hypertension also emerges frequently, linked to chronic vasoconstriction and right ventricular strain.[101] Oral health deteriorates markedly, manifesting as "meth mouth"—characterized by rampant caries, periodontal disease, enamel erosion, and tooth fracture or loss. This stems from xerostomia (reduced saliva flow) due to sympathetic inhibition of salivary glands, bruxism (teeth grinding) from dopaminergic overstimulation, poor hygiene, and acidic oral environment from sugary binges during use.[102] [103] Surveys of users show near-universal gingival recession and abscesses, with extractions often required for advanced cases unresponsive to standard dental interventions.[104] Dermatological lesions, including pruritic sores and ulcers, arise from formication (illusory sensations of insects crawling under skin), prompting compulsive picking and secondary infections. These "meth sores" predominantly affect the face, arms, and extremities, leading to scarring and cellulitis, exacerbated by vasoconstriction-impaired wound healing.[105] [106] Hepatic and renal impairments progress with cumulative exposure, involving ischemia from vasospasm, rhabdomyolysis-induced toxicity, and direct cellular damage via reactive oxygen species. Chronic users display elevated liver enzymes and steatosis, with fulminant failure reported in severe intoxication overlays, while nephrotoxicity manifests as acute kidney injury evolving to chronic kidney disease through glomerular hypertension and tubular necrosis.[107] [108] Cohort analyses confirm accelerated CKD progression in methamphetamine-dependent individuals, independent of comorbidities like hypertension.[109]Route-specific adverse effects
Intranasal administration (insufflation/snorting)
Snorting methamphetamine involves inhaling the powdered or crushed crystalline form through the nose, leading to rapid absorption via the nasal mucosa but also direct exposure of the delicate nasal tissues to the drug's caustic and vasoconstrictive properties. Methamphetamine induces intense vasoconstriction, reducing blood flow and causing ischemia to the nasal mucosa, which can result in tissue necrosis. The sharp crystalline shards also cause mechanical abrasion and micro-trauma to the mucosal lining. Common short-term effects include nasal irritation, burning, epistaxis (nosebleeds), and rhinorrhea. With repeated use, chronic issues develop such as persistent nasal congestion, chronic sinusitis, loss of olfaction (anosmia), crusting, and whistling sounds during breathing due to structural changes. In severe chronic cases, ischemic necrosis can progress to perforation of the nasal septum—a hole in the cartilage dividing the nostrils—potentially leading to saddle-nose deformity, chronic infections, or the need for reconstructive surgery. While intranasal cocaine is more notoriously associated with septal perforation, case reports have documented similar outcomes with methamphetamine insufflation due to comparable mechanisms.[110] Cessation of use is essential to prevent progression, as mild mucosal damage may partially heal, but advanced structural changes like perforation are often permanent without intervention.Neurological and Psychological Consequences
Methamphetamine exerts profound neurotoxic effects primarily through disruption of monoaminergic systems, leading to long-term deficits in dopamine and serotonin neurotransmission. Chronic exposure causes degeneration of dopaminergic terminals in the striatum, evidenced by reductions in dopamine transporter density (DAT) of up to 20-30% in human users.[111] Neuroimaging studies indicate partial recovery from these methamphetamine-induced brain changes after abstinence, with timelines varying by measure: vesicular dopamine levels normalize rapidly within ~10 days; DAT density recovers significantly after protracted abstinence of 9–17 months; brain glucose metabolism shows partial recovery in the thalamus after 12–17 months, but deficits in the striatum often persist; structural gray matter volume (e.g., in the cerebellum) may increase between 6–12 months, though results are mixed and some deficits (e.g., white matter integrity) persist or worsen. Full normalization is uncommon, with many deficits remaining long-term.[112][113][114] Similarly, serotonin transporter (5-HTT) binding is decreased, contributing to axonal damage and neuronal apoptosis in serotonergic pathways.[111] These changes are mediated by methamphetamine-induced hyperthermia, oxidative stress, and excitotoxicity, which elevate extracellular dopamine and glutamate levels, fostering free radical production and mitochondrial dysfunction.[115] Neuroimaging studies reveal structural abnormalities, including greater than normal age-related cortical gray matter loss contributing to accelerated cognitive decline in older users, reduced gray matter volume in the prefrontal cortex, hippocampus, and striatum, correlating with duration and intensity of use.[116][117] Activation of microglia and subsequent neuroinflammation exacerbates methamphetamine's neurotoxicity, with persistent glial response observed in animal models and human postmortem tissue, promoting cytokine release and further neuronal loss.[118] Long-term consequences include impaired gliogenesis and white matter integrity, as demonstrated by decreased oligodendrocyte function and myelin breakdown in chronic users.[119] These alterations increase vulnerability to neurodegenerative conditions, with methamphetamine accelerating dopaminergic neuron loss akin to Parkinson's disease pathology.[120] Psychologically, chronic methamphetamine use induces cognitive deficits across multiple domains, including executive function, memory, and attention, with meta-analyses showing moderate to large effect sizes (Cohen's d ≈ 0.5-1.0) compared to controls, even after prolonged abstinence.[121] Users exhibit impairments in decision-making and inhibitory control, linked to prefrontal dopaminergic hypofunction.[122] Methamphetamine-associated psychosis affects approximately 40% of regular users, manifesting as hallucinations, delusions, and paranoia, often persisting beyond acute intoxication in 10-30% of cases.[123] This psychosis shares phenomenological similarities with schizophrenia but is distinguished by its temporal association with use and potential reversibility with abstinence, though chronic forms may require antipsychotic intervention.[124] Mood disturbances, including depression and anxiety, are prevalent, with rates exceeding 50% in abstinent users, attributed to serotonin depletion and hypothalamic-pituitary-adrenal axis dysregulation.[125] Aggression and violent behavior correlate with reduced serotonin transporter density in the orbitofrontal cortex.[126] Overall, these psychological sequelae impair social functioning and increase suicide risk, underscoring the drug's role in perpetuating a cycle of cognitive and emotional decline.[127]Overdose Mechanisms and Outcomes
Methamphetamine overdose occurs when excessive doses lead to profound sympathomimetic stimulation, primarily through the drug's mechanism of reversing monoamine transporters, causing massive release and reuptake inhibition of dopamine, norepinephrine, and serotonin in the central and peripheral nervous systems.[3] This results in unchecked adrenergic activation, elevating heart rate, blood pressure, and body temperature to dangerous levels, often exceeding 40°C (104°F), which precipitates hyperthermia and metabolic acidosis.[3] [128] Concomitant vasoconstriction and increased myocardial oxygen demand can induce ischemia, arrhythmias, or infarction, while cerebral effects manifest as agitation, psychosis, and seizures due to excitotoxicity from dopamine overflow.[129] Severe physiological derangements in overdose include rhabdomyolysis from prolonged muscle hyperactivity and hyperthermia, leading to acute kidney injury via myoglobinuria and dehydration; disseminated intravascular coagulation may follow from endothelial damage.[3] Respiratory distress arises from aspiration during seizures or coma, compounded by pulmonary edema in some cases.[128] Polydrug involvement, such as with opioids or alcohol, exacerbates respiratory depression or cardiovascular instability, though pure methamphetamine toxicity alone can drive fatal outcomes through cardiac arrest or stroke.[3] Fentanyl contamination in illicit methamphetamine supplies has emerged as a major overdose risk factor, with adjusted prevalence rates of approximately 12.5% in powder forms (often snorted) compared to less than 1% in crystal forms (often smoked).[130][131] Both snorting and smoking fentanyl-laced methamphetamine carry significant overdose hazards due to fentanyl's potency, capable of inducing rapid respiratory depression in trace amounts. While injecting presents the highest overdose risk overall, shifting to snorting or smoking may offer modest risk reduction relative to injection, though overdoses via these routes remain common. Smoking introduces additional dangers, including residue buildup in shared equipment that can lead to unintentional exposure and overdose, particularly for methamphetamine users lacking opioid tolerance. Empirical data do not conclusively demonstrate one route as markedly riskier for fentanyl-contaminated methamphetamine specifically, with both posing extreme threats; harm reduction strategies such as fentanyl test strip use and naloxone carriage are recommended.[132][133] Outcomes range from full recovery with prompt intervention to death or lasting sequelae; prognosis hinges on ingested dose, time to medical care, and comorbidities, with hyperthermia and seizures portending higher mortality.[128] In the United States, age-adjusted methamphetamine-involved overdose death rates rose nearly fivefold from 0.4 to 1.9 per 100,000 between 2012 and 2018, reflecting increased purity and prevalence of use.[82] Treatment is supportive, lacking a specific antidote: benzodiazepines control agitation and seizures, active cooling combats hyperthermia, intravenous fluids address dehydration and rhabdomyolysis, and intubation supports respiration if needed.[3] [129] Survivors may experience persistent psychosis lasting months or permanent neurological deficits like memory impairment from hypoxic brain injury.[128] Fatal methamphetamine overdose from a single isolated oral dose is uncommon, particularly at lower recreational amounts (typically 5–60 mg) in otherwise healthy young adults without tolerance, pre-existing conditions, or co-ingestants. Toxicology literature often cites an approximate lethal oral dose around 200 mg, though well-documented isolated fatalities below this threshold in healthy individuals are rare; when lower-dose deaths occur, they almost always involve complicating factors such as polysubstance use (especially fentanyl adulteration, common in modern illicit supplies), dehydration, extreme exertion/heat, or underlying cardiovascular vulnerabilities. Most methamphetamine-involved deaths reflect chronic or binge patterns leading to cumulative damage (e.g., cardiomyopathy), polysubstance toxicity, or behavioral factors rather than acute single low-dose poisoning. Young, physically fit individuals may have greater resilience to acute sympathomimetic effects due to cardiovascular reserve, though no dose is entirely safe given risks of hyperthermia, arrhythmias, or seizures even at moderate levels. Street product variability adds unpredictability.Addiction Mechanisms
Neurobiological Basis
Methamphetamine exerts its primary neurobiological effects by entering the brain and acting as a potent substrate for the dopamine transporter (DAT), which facilitates its uptake into dopaminergic neurons. Once inside, it promotes the reversal of DAT function, leading to efflux of dopamine into the synaptic cleft, while also disrupting vesicular monoamine transporter 2 (VMAT2) to release dopamine from cytoplasmic vesicles. This results in markedly elevated extracellular dopamine levels, particularly in the mesolimbic pathway projecting from the ventral tegmental area (VTA) to the nucleus accumbens (NAc).[134][135] The surge in dopamine activates D1 and D2 receptors in the NAc, triggering intracellular signaling cascades that induce immediate early gene expression, including c-Fos and its truncated isoform ΔFosB. Unlike transient c-Fos, ΔFosB accumulates with repeated methamphetamine exposure due to its stability and resistance to proteasomal degradation, functioning as a transcription factor that persistently upregulates genes associated with reward sensitivity and synaptic plasticity. This molecular switch contributes to the reinforcement of drug-seeking behavior by enhancing motivational salience of methamphetamine cues.[136][137] Chronic methamphetamine use dysregulates the reward circuitry beyond acute dopamine release, inducing neuroadaptations such as sensitized dopamine release in the striatum and altered glutamate transmission in cortico-accumbens projections. These changes underpin tolerance, where escalating doses are required for euphoria, and dependence, marked by hypodopaminergic states during abstinence that drive compulsive use to restore reward function. Evidence from animal models shows persistent ΔFosB expression correlating with behavioral sensitization and reinstatement of self-administration.[138][139]Genetic and Epigenetic Contributors
Heritability estimates for stimulant use disorders, including methamphetamine dependence, range from 40% to 60%, indicating a substantial genetic component to vulnerability, though specific twin or family studies focused solely on methamphetamine are limited.[140] [141] Genome-wide association studies (GWAS) have identified candidate genes primarily involved in dopamine, serotonin, and glutamate signaling pathways, such as DRD2 (dopamine receptor D2), which shows polymorphisms associated with reduced receptor density and increased risk of dependence; DAT1 (dopamine transporter); BDNF (brain-derived neurotrophic factor), where the Val66Met variant correlates with heightened susceptibility; and SLC6A4 (serotonin transporter), linked to altered serotonin reuptake efficiency.[142] [143] [144] Other implicated loci include COMT (catechol-O-methyltransferase), affecting dopamine metabolism, and CDH13 (cadherin 13), involved in neuronal adhesion and expressed in reward circuitry.[144] [143] These genetic variants contribute to individual differences in reward sensitivity, impulsivity, and neuroadaptation, but effect sizes are modest, and environmental interactions are required for addiction expression.[140] Epigenetic mechanisms, modifiable by methamphetamine exposure, further modulate addiction liability without altering DNA sequence. Methamphetamine induces DNA hypermethylation or hypomethylation at promoters of genes like BDNF and DRD2, suppressing their expression in brain regions such as the nucleus accumbens and prefrontal cortex, thereby exacerbating dopaminergic dysregulation.[145] [146] Histone modifications, including increased acetylation of H3 and H4 tails, facilitate transcriptional changes in reward-related pathways, persisting post-abstinence and contributing to relapse vulnerability.[147] Non-coding RNAs, such as microRNAs targeting DAT1 and SLC6A4, are also dysregulated, influencing synaptic plasticity and craving intensity.[148] These alterations are region-specific, with striatal and accumbal epigenomes showing pronounced shifts after chronic use, underscoring how methamphetamine hijacks endogenous epigenetic machinery to entrench dependence.[149] While promising for biomarkers, human studies remain correlative, and causality requires validation beyond preclinical models.[148]Dependence Development and Withdrawal
Methamphetamine dependence arises from repeated exposure to the drug's potent release of dopamine and other monoamines, prompting neuroadaptations that drive tolerance and compulsive seeking. Chronic use downregulates dopamine transporters and receptors in the striatum, necessitating higher doses to achieve euphoria as the brain compensates for excess neurotransmitter release. [3] This tolerance escalates intake, with animal models showing self-administration doses increasing over days to weeks under extended access conditions. [150] Epigenetic modifications, such as histone acetylation changes in reward-related genes, further entrench these adaptations, contributing to the chronic relapsing nature of addiction. [145] The transition to dependence involves sensitization of certain behaviors alongside tolerance to subjective effects; for instance, locomotor and reward responses intensify due to persistent ΔFosB accumulation in the nucleus accumbens, a transcription factor that alters gene expression to favor drug-seeking over natural rewards. [10] Human studies indicate that even short-term heavy use can produce lasting monoamine depletions, with tolerance to methamphetamine's depleting effects on dopamine persisting 1-2 weeks post-exposure in preclinical models. [151] Dependence severity correlates with dose and duration, with daily users developing compulsive patterns within weeks, as evidenced by epidemiological data linking initiation to rapid progression in vulnerable individuals. [152] Withdrawal from methamphetamine typically includes symptoms such as fatigue, dysphoric mood (depression or anxiety), irritability, insomnia or hypersomnia, increased appetite, psychomotor agitation or retardation, and cravings. These are most pronounced in chronic or dependent users, with an acute phase peaking in the first 7 days and lasting 1-4 weeks, followed by protracted symptoms up to months. The acute "crash" begins within 24 hours of last use, dominated by hypersomnia, hyperphagia, and profound fatigue from dopamine depletion, lasting 2-7 days. [153] This is followed by a subacute phase (7-14 days) with peak dysphoria, including severe depression, anxiety, and irritability, alongside persistent cravings that heighten relapse risk. [153] Protracted withdrawal extends months, featuring anhedonia, cognitive deficits, and mood instability, with suicide ideation elevated due to dopaminergic hypofunction. [154] For occasional or infrequent non-dependent users, withdrawal is often limited to a short "crash" phase (12-24 hours to a few days) with milder symptoms like fatigue, low mood, and lethargy, without the full prolonged syndrome; severity depends on dose, frequency, and individual factors, with true dependence-related withdrawal less likely with infrequent use. Symptom severity overall varies by chronicity of use, with heavy users experiencing more intense and prolonged effects. Management is primarily supportive, including rest, hydration, nutrition, monitoring for severe depression or suicidality, and symptomatic relief (e.g., for sleep or anxiety if needed). No medications are FDA-approved specifically for methamphetamine withdrawal, and evidence for pharmacological treatments is insufficient. [155] Empirical observations confirm that unsupervised withdrawal increases dangers like dehydration from initial hypersomnia and psychosis recurrence, underscoring medical supervision needs. [156]Treatment Approaches
Behavioral Interventions
Behavioral interventions constitute the primary evidence-based approach for treating methamphetamine use disorder (MUD), given the absence of U.S. Food and Drug Administration-approved pharmacotherapies tailored to this condition. These therapies target the modification of maladaptive behaviors, enhancement of coping skills, and reinforcement of abstinence through structured psychological techniques. Systematic reviews highlight contingency management (CM), cognitive behavioral therapy (CBT), and integrated programs like the Matrix Model as the most studied modalities, with CM demonstrating the strongest empirical support for achieving sustained abstinence.[157][158] Contingency management employs operant conditioning principles by offering tangible incentives, such as vouchers or prizes exchangeable for goods, contingent on verified abstinence from methamphetamine, typically confirmed via urine toxicology screens. A 2020 systematic review of 37 randomized controlled trials found CM significantly superior to standard care in promoting abstinence, with participants achieving an average of 7.1 weeks of continuous abstinence compared to 3.1 weeks in control groups. Long-term follow-up studies indicate sustained benefits, including reduced methamphetamine use up to 52 weeks post-treatment, though efficacy diminishes without ongoing reinforcement due to the intervention's finite duration. Implementation challenges persist, including costs associated with incentives and ethical debates over rewarding basic health behaviors, limiting widespread adoption despite its replication across diverse populations.[159][160][161] Cognitive behavioral therapy focuses on identifying and altering thought patterns that perpetuate drug-seeking and use, incorporating skills training for relapse prevention, stress management, and functional analysis of triggers. A systematic review of 13 trials reported CBT associated with significant reductions in methamphetamine use frequency and severity, even in brief formats of 2-4 weeks, alongside improvements in psychological functioning. Meta-analyses of amphetamine-type stimulant dependencies, including methamphetamine, yield moderate effect sizes for abstinence (standardized mean difference -0.28 to -0.69), though outcomes are less robust than CM alone and often require combination with other modalities for optimal results. Acceptance and commitment therapy, a CBT variant, shows comparable efficacy to traditional CBT in reducing dependence and negative consequences over 12-week periods.[162][163][158] The Matrix Model represents an intensive outpatient protocol integrating CBT, motivational interviewing, family education, and urine monitoring, originally developed for stimulant dependencies in the 1980s and validated through multisite trials. Administered over 12-16 weeks with group and individual sessions, it emphasizes relapse prevention planning and social support networks, yielding abstinence rates of 60-70% during treatment in methamphetamine-specific cohorts. A South African adaptation for primary methamphetamine users reported comparable retention and reduced use severity to opioid-focused programs, underscoring its adaptability. Despite these gains, post-treatment relapse remains common, with only 20-30% maintaining long-term abstinence without adjunctive support, highlighting the need for tailored, extended interventions.[164][165][166]Pharmacological Strategies
No medications have received FDA approval specifically for the treatment of methamphetamine use disorder (MUD), leaving pharmacotherapy reliant on off-label agents and experimental compounds with mixed evidence from clinical trials.[167][157] Systematic reviews indicate that while some interventions show modest reductions in methamphetamine use or craving, overall efficacy remains limited, with no single agent demonstrating robust, consistent outcomes across large-scale randomized controlled trials (RCTs).[168][169] Combination therapy with extended-release injectable naltrexone and oral bupropion has emerged as one of the more promising approaches. In a 2019-2020 multicenter RCT involving 403 adults with moderate-to-severe MUD, participants receiving the combination exhibited 27.1% methamphetamine-negative urine samples compared to 10.9% in the placebo group over 12 weeks, alongside improved treatment retention and reduced craving scores.[170] Naltrexone, an opioid antagonist, may mitigate reward pathways dysregulated by methamphetamine, while bupropion, a dopamine-norepinephrine reuptake inhibitor, counters withdrawal-related anhedonia and cognitive deficits; however, gastrointestinal side effects were common, and long-term abstinence rates were not significantly sustained post-treatment.[171] Other investigated agents target neurotransmitter imbalances or neuroplasticity alterations induced by chronic methamphetamine exposure. Modafinil, a wakefulness-promoting agent, has shown preliminary benefits in improving executive function and memory in small trials, potentially aiding cognitive recovery during abstinence, though it did not consistently reduce methamphetamine-positive urine tests in larger studies.[172] Topiramate, an anticonvulsant modulating glutamate and GABA, reduced addiction severity and psychotic symptoms in methamphetamine users with comorbid psychiatric features in a 2024 review, but meta-analyses report only marginal effects on abstinence.[173] Mirtazapine, a noradrenergic and serotonergic antidepressant, alleviated acute withdrawal symptoms like hypersomnia and dysphoria in early-phase trials, yet failed to prevent relapse in follow-up assessments.[174] Gabapentin, alone or in combinations such as the PROMETA protocol with flumazenil, does not significantly reduce methamphetamine use or cravings compared to placebo, as shown in randomized controlled trials.[175][176] Emerging pharmacotherapies under investigation include monoclonal antibodies like IXT-m200, which bind methamphetamine to prolong its elimination half-life and reduce brain penetration, with phase 1/2 trials from 2023 onward demonstrating safety and potential relapse prevention in multiple-dose regimens.[177] Glutamatergic modulators such as ketamine are in ongoing RCTs for craving reduction, while repurposed drugs like riluzole (targeting glutamate release) and methylphenidate (enhancing dopamine signaling) show inconsistent craving suppression in preclinical and small human studies.[178][179] The FDA's 2023 guidance prioritizes development of such novel therapies, emphasizing the need for trials addressing stimulant-specific neurotoxicity, but as of 2025, evidence gaps persist due to high dropout rates and heterogeneous patient populations in MUD studies.[180][181] Pharmacological strategies are thus typically adjunctive to behavioral interventions, with selection guided by individual comorbidities like depression or cognitive impairment rather than standalone efficacy.[182]Relapse Prevention and Outcomes
Contingency management (CM), a behavioral intervention providing tangible rewards for verified abstinence, demonstrates the strongest empirical evidence for reducing methamphetamine use and delaying relapse during treatment. In randomized controlled trials, CM has achieved abstinence rates of up to 50-70% in participants submitting methamphetamine-negative urine samples, outperforming standard counseling alone.[159] However, post-treatment relapse remains common once reinforcements cease, with sustained effects limited without ongoing incentives or integration with other therapies like cognitive-behavioral therapy (CBT).[160] Implementation barriers, including cost and concerns over incentivizing behavior, restrict CM's widespread adoption despite its efficacy in clinical settings.[183] Pharmacological approaches lack FDA-approved options for methamphetamine use disorder, with trials yielding inconsistent results for relapse prevention. Agents like bupropion, modafinil, and mirtazapine have shown modest reductions in use during treatment but fail to produce durable abstinence post-discontinuation.[157] A 2021 National Institutes of Health-funded trial of extended-release naltrexone combined with bupropion reported 13.6% of participants achieving six weeks of continuous abstinence versus 2.5% on placebo, indicating potential but not transformative impact.[171] Animal models suggest promise for compounds targeting dopamine pathways, yet human studies highlight challenges in translating preclinical data to long-term behavioral change.[184] Long-term outcomes reveal high relapse vulnerability, with approximately 40-60% of treated individuals resuming use within three months and over 80% experiencing at least one relapse episode over five years.[185] Predictors of relapse include baseline methamphetamine-positive tests, severe cravings, polysubstance use, and psychosocial stressors, underscoring the interplay of neurobiological dependence and environmental triggers.[186] While integrated programs combining CM, CBT, and recovery coaching yield better retention than monotherapy, absolute abstinence rates remain low at 10-20% beyond one year, reflecting methamphetamine's potent reinforcement properties and the absence of curative pharmacotherapies.[182] Ongoing research emphasizes personalized interventions addressing genetic vulnerabilities and social determinants to improve prognosis.[187]Historical Context
Early Synthesis and Legitimate Applications
Methamphetamine was first synthesized in 1893 by Japanese chemist Nagai Nagayoshi, who produced it in liquid form by reducing ephedrine with red phosphorus and hydroiodic acid.[188][189] This method derived from Nagai's earlier isolation of ephedrine in 1885, marking methamphetamine as a derivative of the natural alkaloid found in Ephedra sinica.[190] The compound's structure, N-methyl-1-phenylpropan-2-amine, consists of two enantiomers: the more potent dextro-methamphetamine and the less active levo form, though early syntheses yielded racemic mixtures.[188] In the early 20th century, methamphetamine saw limited application until Akira Ogata developed a crystallization process in 1919 using phenylacetone and methylamine reduction, enabling production of the pure hydrochloride salt.[188] By the 1930s, it entered pharmaceutical use initially in Japan as a treatment for fatigue, asthma, and narcolepsy, marketed under names like Philopon, with widespread prescription reflecting its stimulant properties in enhancing alertness and reducing appetite.[190] In Germany, methamphetamine was marketed as Pervitin starting in 1938 to enhance alertness and combat fatigue in civilian applications.[191][192] In the United States, methamphetamine hydrochloride, branded as Desoxyn, received FDA approval in 1943 for medical indications including exogenous obesity, narcolepsy, and as a short-term adjunct in attention-deficit hyperactivity disorder (ADHD) management, where it functions by increasing dopamine and norepinephrine release to improve focus and impulse control.[193][3] Legitimate applications persisted post-World War II despite emerging abuse concerns, with Desoxyn prescribed at low doses (typically 5-25 mg daily) for refractory ADHD cases unresponsive to first-line stimulants like methylphenidate, supported by clinical evidence of efficacy in symptom reduction.[6] For obesity, it was used briefly in the mid-20th century to suppress appetite, though long-term risks of tolerance and dependence led to restricted guidelines emphasizing short-term use under medical supervision.[193] These applications underscore methamphetamine's pharmacological value as a central nervous system stimulant when administered in controlled, pharmaceutical-grade forms, distinct from illicit variants due to purity and dosing precision.[3]Military and Wartime Deployment
Methamphetamine, marketed as Pervitin in Germany, was distributed to Wehrmacht personnel starting in 1939 to enhance alertness and endurance during extended operations.[191] The drug facilitated the rapid mechanized advances of the Blitzkrieg in 1940, with over 35 million tablets supplied to troops between April and July of that year alone, including to Luftwaffe pilots and Panzer crews who logged thousands of hours without sleep.[191] [194] Distribution was framed as a medical countermeasure against fatigue rather than a tool for ideological enhancement, though side effects like psychological crashes and dependency emerged, contributing to operational strains later in the war.[195] In Japan, methamphetamine under the brand Philopon was synthesized earlier and deployed by the Imperial military from the late 1930s onward to sustain soldier performance in grueling Pacific campaigns.[196] Troops, including kamikaze pilots, received injections or tablets to suppress fear, hunger, and fatigue, enabling prolonged combat readiness amid resource shortages.[197] Postwar surpluses of military stockpiles flooded civilian markets, exacerbating addiction epidemics, but wartime use prioritized tactical stamina over long-term health.[198] Allied forces primarily relied on amphetamine variants like Benzedrine rather than methamphetamine, though intelligence confirmed Axis reliance on Pervitin by 1941, prompting concerns over similar performance edges.[199] Limited U.S. military adoption of methamphetamine occurred during the Korean War for analogous alertness purposes, but documentation emphasizes its secondary role compared to broader amphetamine distribution.[197]Regulatory Evolution and Illicit Shift
![Desoxyn_Package_of_100_Pills.jpg][float-right] Methamphetamine was initially approved for medical use in the United States, with the FDA granting approval for methamphetamine hydrochloride (branded as Desoxyn) in 1943 for conditions such as narcolepsy and obesity.[8] Legal production continued through the 1950s and 1960s, prescribed for weight loss, alertness, and attention disorders, but widespread availability contributed to rising recreational abuse and diversion.[200] By the late 1960s, concerns over dependency and public health impacts prompted stricter controls, culminating in the Comprehensive Drug Abuse Prevention and Control Act of 1970, which classified methamphetamine as a Schedule II controlled substance under the Controlled Substances Act, acknowledging its high abuse potential alongside limited accepted medical uses.[8][201] The scheduling significantly curtailed legal injectable forms, reducing legitimate supply and initially diminishing overall use, but it inadvertently spurred the growth of illicit manufacturing.[201] In the 1970s, as federal restrictions limited pharmaceutical production, clandestine laboratories proliferated, primarily producing racemic methamphetamine via phenyl-2-propanone (P2P) methods, often operated by outlaw motorcycle gangs.[202] Abuse escalated in the 1980s with influxes of higher-purity d-methamphetamine smuggled from Mexico, prompting further regulatory measures targeting precursors: the Chemical Diversion and Trafficking Act of 1988 listed ephedrine as a List I chemical, followed by tightened controls in 1995 and 1997.[203] The Comprehensive Methamphetamine Control Act of 1996 expanded restrictions on imports and domestic production of precursor chemicals.[204] By the early 2000s, domestic "shake-and-bake" labs using over-the-counter pseudoephedrine dominated small-scale production, fueling a rural U.S. epidemic, until the Combat Methamphetamine Epidemic Act of 2005 imposed federal limits on pseudoephedrine sales, requiring identification and record-keeping behind pharmacy counters.[205][206] This shift dismantled most U.S. labs, redirecting supply to large-scale Mexican cartel operations producing high-purity crystal methamphetamine via P2P methods, which evaded U.S. precursor controls through international smuggling.[8] Despite ongoing medical prescriptions for ADHD and obesity under strict Schedule II protocols, the illicit market now overshadows legitimate use, with purity levels often exceeding 90% in seized products, compared to earlier diluted street forms.[8] These regulations, while reducing domestic synthesis hazards, have concentrated production in jurisdictions with weaker enforcement, perpetuating global trafficking networks.[206]Production and Distribution
Clandestine Manufacturing Trends
Clandestine methamphetamine production in the United States has undergone a profound shift from domestic small-scale operations to large-scale manufacturing dominated by Mexican cartels. Prior to the mid-2000s, illicit labs primarily utilized the red phosphorus method, extracting ephedrine or pseudoephedrine from over-the-counter cold medications to produce d-methamphetamine in multipound quantities of high purity.[19] This approach proliferated in rural and residential areas, particularly in the West and Southwest, with thousands of lab seizures annually reported by authorities.[207] The passage of the Combat Methamphetamine Epidemic Act in 2006 imposed strict controls on pseudoephedrine sales, prompting manufacturers to adapt by seeking alternative precursors or relocating production.[203] This led to a temporary rise in domestic labs using alternative methods, but ultimately accelerated a transition to the phenyl-2-propanone (P2P) method, which relies on P2P and methylamine—chemicals less restricted at the time and amenable to industrial-scale synthesis.[203] By the 2010s, Mexican trafficking organizations established "superlabs" capable of producing hundreds of pounds per cycle, exporting finished product across the U.S. border, where methamphetamine seizures escalated dramatically, from 266,828 pounds between FY2012 and FY2018 to record volumes in subsequent years.[208] [209] Domestic U.S. lab seizures have since plummeted, reflecting the near-total displacement by Mexican imports; the DEA's El Paso Intelligence Center recorded only 60 clandestine meth lab events in 2023, a stark decline from peaks exceeding 20,000 in the early 2000s.[210] Mexican production now yields crystalline methamphetamine of consistently high purity, typically exceeding 90%, with no official unified grading or quality classification standards; DEA analyses of seized samples reported an average purity of 96.7% in late 2022, and the majority exceeding 95%, while levels above 80% are generally considered relatively pure and crystal forms significantly surpass powders or tablets, which may contain less than 10% in lower-quality instances.[211] [212]using sophisticated equipment and precursors like those shipped from Asia, enabling cartel dominance in supply chains. While sporadic small-scale U.S. labs persist, often in response to fentanyl market dynamics, they represent a negligible fraction of output compared to cartel-scale operations.[213] This evolution underscores the limitations of precursor controls in curbing adaptable illicit networks, as traffickers exploit global chemical trade vulnerabilities.[214]Global Trafficking Networks
Methamphetamine trafficking is dominated by large-scale organized crime groups operating from primary production hubs in Mexico and Southeast Asia's Golden Triangle region, with precursors often sourced from China and India. Mexican cartels, particularly the Sinaloa Cartel and Cartel Jalisco Nueva Generación (CJNG), produce the majority of methamphetamine destined for the United States, accounting for over 80% of U.S. supply through cross-border smuggling via tunnels, vehicles, and maritime routes. [215] These groups have expanded globally, exporting to high-value markets like Australia and Japan, where CJNG-linked seizures indicate wholesale distribution adapting to local demand. [216] In Asia, production centers in Myanmar's Shan State within the Golden Triangle drive trafficking to East and Southeast Asia, with organized crime syndicates utilizing overland routes through Laos and Thailand before maritime shipment to Australia and Pacific islands. [217] Seizures of methamphetamine in East and Southeast Asia reached a record 236 tons in 2024, a 24% increase from 2023, reflecting expanded laboratory capacity post-Myanmar's 2021 military coup, which quadrupled per-case crystal meth hauls. [218] [219] Emerging networks in Afghanistan, leveraging ephedra-based synthesis, have surged methamphetamine exports via the Balkan Route to Europe and the Indian subcontinent, with UNODC reporting rapid expansion as heroin flows decline. [220] Globally, traffickers conceal shipments in legitimate trade, such as contaminated avocado oil or electronics, while precursor chemicals like those for P2P synthesis flow from Asia to Mexican labs; U.S. authorities seized 300,000 kilograms of such precursors from China bound for Sinaloa in September 2025. [221] Mexican operations dismantled 42 tons of methamphetamine in clandestine labs in June 2025, valued at over $50 million, underscoring the scale of industrial-scale production fueling international distribution. [222] Trafficking adaptability exploits conflicts and trade vulnerabilities, with UNODC noting record global amphetamine-type stimulant seizures in 2023—nearly half of all synthetic drug intercepts—driven by convergent routes for methamphetamine and similar synthetics like captagon. [83] Mexican groups' vertical integration, from precursor importation to wholesale export, has positioned them as primary global suppliers, while Asian networks maintain regional dominance amid rising domestic consumption. [223]Supply Reduction Efforts
Supply reduction efforts targeting methamphetamine primarily focus on disrupting production, precursor chemical diversion, and trafficking networks, with the United States Drug Enforcement Administration (DEA) emphasizing interdiction of imports from Mexican cartels responsible for over 90% of U.S. supply.[224] The DEA's Chemical Control Program aims to reduce illicit drug supply by monitoring and regulating chemicals like ephedrine and pseudoephedrine, which were subjected to stricter controls under the Combat Methamphetamine Epidemic Act of 2005, leading to a 75% decline in domestic methamphetamine laboratories from 2004 to 2010.[225] [226] These domestic measures shifted production to large-scale "superlabs" in Mexico operated by cartels such as Sinaloa and Cartel Jalisco Nueva Generación (CJNG), prompting bilateral initiatives like Operation Crystal Shield launched in 2020, which targeted eight U.S. transportation hubs including Atlanta and Los Angeles, resulting in thousands of arrests and seizures exceeding 100,000 pounds of methamphetamine in its initial phase.[227] [224] Internationally, efforts center on precursor chemical controls under the 1988 United Nations Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances, administered by the International Narcotics Control Board (INCB) and UNODC, which track substances like phenyl-2-propanone (P2P) and monitor exports from primary sources including China and India.[228] U.S. agencies have intensified maritime interdictions, seizing over 300,000 kilograms of meth precursors shipped from China to Mexico's Sinaloa Cartel in 2025, alongside 50,000 kilograms in another operation, disrupting potential production of billions of doses.[221] [229] In 2024, U.S. Customs and Border Protection reported methamphetamine seizures surpassing 55,000 pounds in August alone, reflecting a 37% year-over-year increase, while DEA seizures of methamphetamine pills rose from 2.6 million units in 2023 to 3.2 million in 2024.[230] [224] The 2025 launch of Project Portero targets cartel "gatekeepers" facilitating precursor flows, aiming to dismantle logistics networks.[231] Despite these interventions, supply resilience persists due to cartels' adaptability, including substitution of precursors and expansion into new synthetic methods, with Mexican production capacity estimated to exceed U.S. demand by factors of 10 or more.[224] Empirical analyses indicate precursor restrictions yielded temporary reductions in domestic U.S. methamphetamine purity and consumption in the mid-2000s, correlating with lower treatment admissions and crime rates, but long-term efficacy diminished as imports filled the gap, maintaining high street purity above 90% since 2012.[226] [232] Australian studies of supply disruptions similarly show short-term declines in methamphetamine-related harms, such as reduced hospital presentations, but underscore that sustained reductions require addressing international precursor trade vulnerabilities.[233] Overall, while seizures and controls have curbed small-scale domestic output, they have not appreciably lowered U.S. methamphetamine availability, as evidenced by stable or rising overdose involvements when mixed with fentanyl.[224][234]Policy and Legal Framework
Scheduling and Penalties
In the United States, methamphetamine is classified as a Schedule II controlled substance under the Controlled Substances Act (CSA) of 1970, as amended, signifying a high potential for abuse with severe psychological or physical dependence liability, but also accepted medical uses with restrictions to prevent abuse.[235] This scheduling accommodates limited therapeutic applications, such as short-term treatment of attention-deficit/hyperactivity disorder (ADHD) and exogenous obesity via prescription formulations like Desoxyn tablets.[8] The Drug Enforcement Administration (DEA) enforces this classification, prohibiting non-medical production, distribution, or possession, while authorizing DEA-registered entities for legitimate pharmaceutical handling.[193] Federal penalties for methamphetamine offenses are codified primarily in 21 U.S.C. § 841 and escalate based on quantity, prior convictions, and outcomes like death or serious injury from use. Simple possession under 21 U.S.C. § 844 carries up to one year imprisonment and a minimum $1,000 fine for first offenses, doubling to two years and $2,500 for subsequent ones, though federal charges often arise in trafficking contexts rather than isolated personal use. Trafficking penalties impose mandatory minimum sentences for distribution, manufacturing, or dispensing, with enhancements for methamphetamine due to its Schedule II status and purity thresholds.| Quantity Threshold (Pure Methamphetamine) | First Offense Penalty | Second or Subsequent Offense Penalty |
|---|---|---|
| Less than 5 grams | 0–40 years; fine up to $5 million (individual) or $25 million (organization) | 0–life; same fines |
| 5 grams or more | 5–40 years; same fines | 10–life; same fines |
| 50 grams or more | 10–life; same fines | 20–life; same fines |
| Any amount if death or serious injury results | 20–life; same fines | 20–life; same fines |