Levomethamphetamine (INN: levmetamfetamine) is an optical isomer of methamphetamine primarily used as a topical nasal decongestant. Levomethamphetamine is used to treat nasal congestion from allergies and the common cold. It was first used medically as decongestant beginning in 1958 and has been used for such purposes, primarily in the United States, since then.

Levomethamphetamine is significantly less potent in terms of physiologic and subjective drug effects than racemic methamphetamine, dextromethamphetamine, and related amphetamines, especially when used as a nasal decongestant at therapeutic doses.

Levomethamphetamine is used to treat nasal congestion related to the common cold and allergic rhinitis. It is available in the form of an inhaler containing 50 mg total per inhaler and delivering between 0.04 and 0.15 mg of the drug per inhalation. Inhalers with a total of 113 mg levomethamphetamine were previously marketed in the United States, but the total amount was eventually reduced to 50 mg.

When the nasal decongestant is taken in excess, levomethamphetamine has potential side effects. These would be similar to those of other decongestants.

Levomethamphetamine acts as a selective norepinephrine releasing agent. The potencies of levomethamphetamine, levoamphetamine, dextromethamphetamine, and dextroamphetamine in terms of norepinephrine release in vitro and in vivo in rats are all similar.

Conversely, whereas dextromethamphetamine and dextroamphetamine are relatively balanced releasers of dopamine and norepinephrine in vitro, levomethamphetamine is about 15- to 20-fold less potent in inducing dopamine release relative to norepinephrine release. Moreover, whereas levoamphetamine is about 3- to 5-fold less potent in terms of dopamine release than dextroamphetamine in vivo, levomethamphetamine is dramatically less potent than dextromethamphetamine and substantially less potent than levoamphetamine in this regard.

In accordance with the findings of catecholamine release studies, levomethamphetamine is 2- to 10-fold or more less potent than dextromethamphetamine in terms of psychostimulant-like effects in rodents. For comparison, levoamphetamine is only 1- to 4-fold less potent than dextroamphetamine in its stimulating and reinforcing effects in monkeys and humans.

The effects of levomethamphetamine are qualitatively distinct relative to those of racemic methamphetamine and dextromethamphetamine and it does not possess the same potential for euphoria or addiction that these drugs possess. In clinical studies, levomethamphetamine at oral doses of 1 to 10 mg has been found not to affect subjective drug responses, heart rate, blood pressure, core temperature, electrocardiography, respiration rate, oxygen saturation, or other clinical parameters. As such, doses of levomethamphetamine of less than or equal to 10 mg have no significant physiological or subjective effects. However, higher doses of levomethamphetamine, for instance 0.25 to 0.5 mg/kg (mean doses of ~18–37 mg) intravenously, have been reported to produce significant pharmacological effects, including increased heart rate and blood pressure, increased respiration rate, and subjective effects like intoxication and drug liking. On the other hand, in contrast to dextromethamphetamine, levomethamphetamine also produces subjective "bad" or aversive drug effects. Among the physiological effects of levomethamphetamine is vasoconstriction, which makes it useful for nasal decongestion.