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Flibanserin
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| Clinical data | |
|---|---|
| Trade names | Addyi |
| AHFS/Drugs.com | Monograph |
| MedlinePlus | a615040 |
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| Routes of administration | By mouth |
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| Pharmacokinetic data | |
| Bioavailability | 33%[3] |
| Protein binding | ~98% |
| Metabolism | Extensive by liver (mainly by CYP3A4 and CYP2C19) |
| Elimination half-life | ~11 hours |
| Excretion | Bile duct (51%), kidney (44%) |
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| IUPHAR/BPS | |
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| ChemSpider | |
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| KEGG | |
| ChEBI | |
| ChEMBL | |
| CompTox Dashboard (EPA) | |
| ECHA InfoCard | 100.170.970 |
| Chemical and physical data | |
| Formula | C20H21F3N4O |
| Molar mass | 390.410 g·mol−1 |
| 3D model (JSmol) | |
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Flibanserin, sold under the brand name Addyi, is a medication approved for the treatment of pre-menopausal women with hypoactive sexual desire disorder (HSDD).[4][5] The medication attempts to improve sexual desire, increase the number of satisfying sexual events, and decrease the distress associated with low sexual desire.[3] The most common side effects are dizziness, sleepiness, nausea, difficulty falling asleep or staying asleep and dry mouth.[3]
Development by Boehringer Ingelheim was halted in October 2010, following a negative evaluation by the US Food and Drug Administration (FDA).[6] The rights to the drug were then transferred to Sprout Pharmaceuticals, which achieved approval of the drug by the US FDA in August 2015.[7] Addyi is approved for medical use in the United States for premenopausal women with hypoactive sexual desire disorder and in Canada for premenopausal and postmenopausal women with hypoactive sexual desire disorder.[3][8]
Hypoactive sexual desire disorder was recognized as a distinct sexual function disorder for more than 30 years, but was removed from the Diagnostic and Statistical Manual of Mental Disorders in 2013, and replaced with a new diagnosis called female sexual interest/arousal disorder (FSIAD).[9][10]
Medical uses
[edit]Flibanserin is indicated for the treatment of premenopausal women with acquired, generalized hypoactive sexual desire disorder as characterized by low sexual desire that causes marked distress or interpersonal difficulty[3] and is NOT due to: a co-existing medical or psychiatric condition;[3] problems within the relationship,[3] or the effects of a medication or other drug substance.[3]
The effectiveness of flibanserin was evaluated in three phase III clinical trials. Each of the three trials had two co-primary endpoints, one for satisfying sexual events (SSEs) and the other for sexual desire. Each of the three trials also had a secondary endpoint that measured distress related to sexual desire. All three trials showed that flibanserin produced an increase in the number of satisfying sexual events and reduced distress related to sexual desire. The first two trials used an electronic diary to measure sexual desire, and did not find an increase. These two trials also measured sexual desire using the Female Sexual Function Index (FSFI) as a secondary endpoint, and an increase was observed using this latter measure. The FSFI was used as the co-primary endpoint for sexual desire in the third trial, and again showed a statistically significant increase.[3]
Supportive analyses based on the patient's perspective of her symptoms at the end of the study showed that improvements in symptoms of hypoactive sexual desire disorder were not only statistically significant but also clinically meaningful to women.[11]
Side effects
[edit]The US prescription label contains a boxed warning for hypotension and syncope in certain settings.[3]
The majority of adverse events are mild to moderate in severity. The most commonly reported adverse events included dizziness, nausea, feeling tired, sleepiness, and trouble sleeping.[3]
Drinking alcohol while on flibanserin may increase the risk of severe low blood pressure.[3]
Mechanism of action
[edit]Activity profile
[edit]Flibanserin acts as a full agonist in the frontal cortex and the Dorsal Raphe Nucleus, but only as a partial agonist in the CA3 region of the hippocampus[12] of the 5-HT1A receptor (serotonin receptor) (Ki = 1 nM in CHO cells, but only 15–50 nM in cortex, hippocampus and dorsal raphe)[4] and, with lower affinity, as an antagonist of the 5-HT2A receptor (Ki = 49 nM) and antagonist or very weak partial agonist of the D4 receptor (Ki = 4–24 nM,[13] Ki = 8–650 nM[14]).[15][16][17] Flibanserin demonstrates selectivity for postsynaptic 5-HT1A receptors.[17][18] Despite the much greater affinity of flibanserin for the 5-HT1A receptor, and for reasons that are unknown (although it might be caused by the competition with endogenous serotonin), flibanserin occupies the 5-HT1A and 5-HT2A receptors in vivo with similar percentages.[4][19] Flibanserin also has low affinity for the 5-HT2B receptor (Ki = 89.3 nM) and the 5-HT2C receptor (Ki = 88.3 nM), both of which it behaves as an antagonist of.[17] Flibanserin preferentially activates 5-HT1A receptors in the prefrontal cortex, demonstrating regional selectivity, and has been found to increase dopamine and norepinephrine levels and decrease serotonin levels in the rat prefrontal cortex, actions that were determined to be mediated by activation of the 5-HT1A receptor.[15] As such, flibanserin has been described as a norepinephrine–dopamine disinhibitor (NDDI).[17][20]
The proposed mechanism of action refers to the Kinsey dual control model of sexual response.[21] Various neurotransmitters, sex steroids, and other hormones have important excitatory or inhibitory effects on the sexual response. Among neurotransmitters, excitatory activity is driven by dopamine and norepinephrine, while inhibitory activity is driven by serotonin. The balance between these systems is of significance for a normal sexual response. By modulating serotonin and dopamine activity in certain parts of the brain, flibanserin may improve the balance between these neurotransmitter systems in the regulation of sexual response.[22][23]
Society and culture
[edit]Flibanserin was originally developed as an antidepressant,[24][15] but was found to have pro-sexual effects and was later repurposed for the treatment of hypoactive sexual desire disorder.[medical citation needed]
Names
[edit]Flibanserin is sold under the brand name Addyi.[3]
Approval process and advocacy
[edit]In June 2010, a federal advisory panel to the US Food and Drug Administration (FDA) unanimously voted against recommending approval of flibanserin, citing an inadequate risk-benefit ratio. The committee acknowledged the validity of hypoactive sexual desire as a diagnosis, but expressed concern with the drug's side effects and insufficient evidence for efficacy, especially the drug's failure to show a statistically significant effect on the co-primary endpoint of sexual desire.[25] Ahead of the votes, Boehringer Ingelheim had mounted a publicity campaign to promote the controversial disorder of "hypoactive sexual desire".[26] In 2010, the FDA issued a Complete Response Letter, stating that the new drug application could not be approved in its current form. The letter cited several concerns, including the failure to demonstrate a statistical effect on the co-primary endpoint of sexual desire and overly restrictive entry criteria for the two phase III trials. The FDA recommended performing a new phase III trial with less restrictive entry criteria.[27] In October 2010, Boehringer announced that it would discontinue its development of flibanserin in light of the FDA's decision.[28]
Sprout responded to the FDA's cited deficiencies and refiled the new drug application in 2013. The submission included data from a new phase III trial and several phase I drug-drug interaction studies.[27][29] The FDA again refused the application, citing an uncertain risk/benefit ratio. In December 2013, a Formal Dispute Resolution was filed,[30] which contained the requirements of the FDA for further studies. These include two studies in healthy subjects to determine if flibanserin impairs their ability to drive, and to determine if it interferes with other biochemical pathways. The Agency agreed to call a new Advisory Committee meeting to consider whether the risk-benefit ratio of flibanserin was favorable after this additional data was obtained.[30][31][32]
In June 2015, the US FDA Advisory Committee, which includes the Bone, Reproductive, and Urologic Drugs Advisory Committee (BRUDAC) and the Drug Safety and Risk Management Advisory Committee (DSRM), recommended approval of the drug by 18–6, with the proviso that measures be taken to inform women of the drug's side effects.[33][34] On 18 August 2015, the FDA approved Addyi (Flibanserin) for the treatment of premenopausal women with low sexual desire that causes personal distress or relationship difficulties. The approval specified that flibanserin should not be used to treat low sexual desire caused by co-existing psychiatric or medical problems; low sexual desire caused by problems in the relationship; or low sexual desire due to medication side effects.[3]
As of August 2015, Sprout Pharmaceuticals had not yet made an application to the European Medicines Agency for a marketing authorization.[35]
Advocacy groups
[edit]Even the Score, a coalition of women's groups brought together by a Sprout consultant, actively campaigned for the approval of flibanserin. The campaign emphasized that several approved treatments for male sexual dysfunction exist, while no such treatment for women was available.[36] The group successfully obtained letters of support from the President of the National Organization for Women, the editor of the Journal of Sexual Medicine, and several members of Congress.[37]
Other organizations supporting the approval of flibanserin included the National Council of Women's Organizations, the Black Women's Health Imperative, the Association of Reproductive Health Professionals, National Consumers League, and the American Sexual Health Association.[38][39][40][41]
The approval was opposed by the National Women's Health Network, the National Center for Health Research and Our Bodies Ourselves.[42] A representative of PharmedOut said "To approve this drug will set the worst kind of precedent — that companies that spend enough money can force the FDA to approve useless or dangerous drugs."[43] An editorial in JAMA noted that, "Although flibanserin is not the first product to be supported by a consumer advocacy group in turn supported by pharmaceutical manufacturers, claims of gender bias regarding the FDA's regulation have been particularly noteworthy, as have the extent of advocacy efforts ranging from social media campaigns to letters from members of Congress".[44]
Acquisition by Valeant Pharmaceuticals
[edit]In August 2015, Valeant Pharmaceuticals and Sprout Pharmaceuticals announced that Valeant will acquire Sprout, on a debt-free basis, for approximately $1 billion in cash, plus a share of future profits based upon the achievement of certain milestones.[45]
Reception
[edit]The initial response since the 2015 introduction of flibanserin to the US market was slow with 227 prescriptions written during the first three weeks.[46] The slow response may be related to a number of factors: physicians require about 10 minutes of online training to get certified; the medication costs about US$400 per month;[47] and questions about the drug's efficacy and need.[46]
References
[edit]- ^ "Regulatory Decision Summary for Addyi". Health Canada. 27 February 2018. Archived from the original on 7 June 2022. Retrieved 7 June 2022.
- ^ "Details for: Addyi". Drug and Health Products Portal. 8 April 2022. Retrieved 30 June 2025.
- ^ a b c d e f g h i j k l m n o "Addyi- flibanserin tablet, film coated". DailyMed. 10 October 2019. Archived from the original on 20 October 2020. Retrieved 20 October 2020.
- ^ a b c Borsini F, Evans K, Jason K, Rohde F, Alexander B, Pollentier S (2002). "Pharmacology of flibanserin". CNS Drug Reviews. 8 (2): 117–142. doi:10.1111/j.1527-3458.2002.tb00219.x. PMC 6741686. PMID 12177684.
- ^ Jolly E, Clayton A, Thorp J, Lewis-D'Agostino D, Wunderlich G, Lesko L (April 2008). "Design of Phase III pivotal trials of flibanserin in female Hypoactive Sexual Desire Disorder (HSDD)". Sexologies. 17 (Suppl 1): S133–4. doi:10.1016/S1158-1360(08)72886-X.
- ^ Spiegel online: Pharmakonzern stoppt Lustpille für die Frau Archived 1 February 2012 at the Wayback Machine, 8 October 2010 (in German)
- ^ Mullard A (October 2015). "FDA approves female sexual dysfunction drug". Nature Reviews. Drug Discovery. 14 (10): 669. doi:10.1038/nrd4757. PMID 26424353. S2CID 36380932.
- ^ "Addyi Product Monograph" (PDF). Health Canada. 26 January 2021. Archived (PDF) from the original on 14 November 2022. Retrieved 14 November 2022.
- ^ American Psychiatric Association. Sexual and gender identity disorders. In: American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders. 4th ed. Washington, DC: American Psychiatric Association; 2000:493–538.
- ^ Nagoski E (27 February 2015). "Nothing Is Wrong With Your Sex Drive". The New York Times. Archived from the original on 15 July 2017. Retrieved 31 July 2017.
- ^ Simon JA, Clayton AH, Kim NN, Patel S (February 2022). "Clinically Meaningful Benefit in Women with Hypoactive Sexual Desire Disorder Treated with Flibanserin". Sexual Medicine. 10 (1) 100476. doi:10.1016/j.esxm.2021.100476. PMC 8847820. PMID 34999484.
- ^ Rueter LE, de Montigny C, Blier P (August 1998). "In vivo electrophysiological assessment of the agonistic properties of flibanserin at pre- and postsynaptic 5-HT1A receptors in the rat brain". Synapse. 29 (4): 392–405. doi:10.1002/(SICI)1098-2396(199808)29:4<392::AID-SYN11>3.0.CO;2-T. PMID 9661257. S2CID 23093139.
- ^ Borsini F, Evans K, Jason K, Rohde F, Alexander B, Pollentier S (2002). "Pharmacology of flibanserin". CNS Drug Reviews. 8 (2): 117–142. doi:10.1111/j.1527-3458.2002.tb00219.x. PMC 6741686. PMID 12177684.
- ^ Stahl SM (February 2015). "Mechanism of action of flibanserin, a multifunctional serotonin agonist and antagonist (MSAA), in hypoactive sexual desire disorder". CNS Spectrums. 20 (1): 1–6. doi:10.1017/S1092852914000832. PMID 25659981.
- ^ a b c Invernizzi RW, Sacchetti G, Parini S, Acconcia S, Samanin R (August 2003). "Flibanserin, a potential antidepressant drug, lowers 5-HT and raises dopamine and noradrenaline in the rat prefrontal cortex dialysate: role of 5-HT(1A) receptors". British Journal of Pharmacology. 139 (7): 1281–1288. doi:10.1038/sj.bjp.0705341. PMC 1573953. PMID 12890707.
- ^ Borsini F, Giraldo E, Monferini E, Antonini G, Parenti M, Bietti G, et al. (September 1995). "BIMT 17, a 5-HT2A receptor antagonist and 5-HT1A receptor full agonist in rat cerebral cortex". Naunyn-Schmiedeberg's Archives of Pharmacology. 352 (3): 276–282. doi:10.1007/bf00168557. PMID 8584042. S2CID 19340842.
- ^ a b c d Stahl SM, Sommer B, Allers KA (January 2011). "Multifunctional pharmacology of flibanserin: possible mechanism of therapeutic action in hypoactive sexual desire disorder". The Journal of Sexual Medicine. 8 (1): 15–27. doi:10.1111/j.1743-6109.2010.02032.x. PMID 20840530.
- ^ English C, Muhleisen A, Rey JA (April 2017). "Flibanserin (Addyi): The First FDA-Approved Treatment for Female Sexual Interest/Arousal Disorder in Premenopausal Women". P & T. 42 (4): 237–241. PMC 5358680. PMID 28381915.
- ^ Scandroglio A, Monferini E, Borsini F (February 2001). "Ex vivo binding of flibanserin to serotonin 5-HT1A and 5-HT2A receptors". Pharmacological Research. 43 (2): 179–183. doi:10.1006/phrs.2000.0762. PMID 11243720.
- ^ Stahl SM (17 March 2008). Stahl's Essential Psychopharmacology: Neuroscientific Basis and Practical Applications. Cambridge University Press. p. 658. ISBN 978-0-521-67376-1. Retrieved 23 April 2012.
- ^ Janssen, E, Bancroft J. The dual control model: The role of sexual inhibition & excitation in sexual arousal and behavior In Janssen, E. (Ed). (2006). The Psychophysiology of Sex. Bloomington, IN:Indiana University press.
- ^ Pfaus JG (June 2009). "Pathways of sexual desire". The Journal of Sexual Medicine. 6 (6): 1506–1533. doi:10.1111/j.1743-6109.2009.01309.x. PMID 19453889. S2CID 3427784.
- ^ Allers KA, Dremencov E, Ceci A, Flik G, Ferger B, Cremers TI, et al. (May 2010). "Acute and repeated flibanserin administration in female rats modulates monoamines differentially across brain areas: a microdialysis study". The Journal of Sexual Medicine. 7 (5): 1757–1767. doi:10.1111/j.1743-6109.2010.01763.x. PMID 20163532.
- ^ D'Aquila P, Monleon S, Borsini F, Brain P, Willner P (December 1997). "Anti-anhedonic actions of the novel serotonergic agent flibanserin, a potential rapidly-acting antidepressant". European Journal of Pharmacology. 340 (2–3): 121–132. doi:10.1016/S0014-2999(97)01412-X. PMID 9537806.
- ^ "18 June 2010 meeting of the FDA Advisory Committee for Reproductive Health Drugs" (PDF). Archived from the original (PDF) on 13 September 2016. Retrieved 18 November 2015.
- ^ "Drug for sexual desire disorder opposed by panel". The New York Times. 18 June 2010. Archived from the original on 11 February 2021. Retrieved 24 February 2017.
- ^ a b "Joint Meeting of the Bone, Reproductive and Urologic Drugs Advisory Committee (BRUDAC) and the Drug Safety and Risk Management (DSaRM) Advisory Committee" (PDF). Food and Drug Administration. Archived from the original (PDF) on 5 June 2015.
- ^ Burger L (8 October 2010). "Boehringer pulls the plug on "pink Viagra"". Reuters. Archived from the original on 15 October 2010. Retrieved 1 July 2017.
- ^ "Sprout Pharmaceuticals resubmits flibanserin NDA for treating HSDD in pre-menopausal women". 27 June 2013. Archived from the original on 19 March 2025. Retrieved 29 April 2025.
- ^ a b "ADDYI® (flibanserin) - Home". Sprout. Archived from the original on 10 August 2015. Retrieved 31 July 2017.
- ^ FDA seeks more tests on a female Viagra, by Matthew Perrone, The Detroit Free Press, page 2A Wednesday, 12 February 2014
- ^ Landau E (11 February 2014). "FDA: Female sex drive drug needs more research - CNN.com". CNN. Archived from the original on 1 August 2017. Retrieved 31 July 2017.
- ^ Stein R (4 June 2015). "Advisers To FDA Recommend Agency Approve Drug To Boost Female Libido". NPR. Archived from the original on 4 June 2015. Retrieved 4 June 2015.
- ^ "Critics: Women's Sex Pill Approval Vote Driven By PR, Not Science". Forbes. 7 June 2015. Archived from the original on 4 March 2021. Retrieved 28 August 2017.
- ^ Torjesen I (21 August 2015). "First drug to improve sexual desire in women approved in the United States". The Pharmaceutical Journal. 295 (7878). doi:10.1211/PJ.2015.20069201.
- ^ Pollack A (4 June 2015). "'Viagra for Women' Is Backed by an F.D.A. Panel". The New York Times. Archived from the original on 13 February 2021. Retrieved 24 February 2017.
- ^ "Why Flibanserin Is Not the 'Female Viagra'". The Atlantic. 19 August 2015. Archived from the original on 7 April 2021. Retrieved 7 March 2017.
- ^ Pollack A (18 August 2015). "F.D.A. Approves Addyi, a Libido Pill for Women". The New York Times. Archived from the original on 26 March 2021. Retrieved 24 February 2017.
- ^ "Association of Reproductive Health Professionals". Archived from the original on 18 November 2015. Retrieved 17 November 2015.
- ^ "National Consumers League". 4 June 2015. Archived from the original on 18 November 2015. Retrieved 17 November 2015.
- ^ "American Sexual Health Association". 19 August 2015. Archived from the original on 6 November 2015. Retrieved 17 November 2015.
- ^ "Raleigh's Sprout Pharmaceuticals awaits FDA ruling on female libido drug | News & Observer". Archived from the original on 3 June 2019. Retrieved 18 November 2015.
- ^ Perry P (8 June 2015). "'Faux-advocacy,' not science, prompted FDA panel's OK of 'low libido' drug for women, critics charge". minnpost.com. Archived from the original on 30 August 2015. Retrieved 18 August 2015.
- ^ Gellad WF, Flynn KE, Alexander GC (September 2015). "Evaluation of Flibanserin: Science and Advocacy at the FDA". JAMA. 314 (9): 869–870. doi:10.1001/jama.2015.8405. PMID 26148201.
- ^ "Valeant - Valeant Pharmaceuticals to Acquire Sprout Pharmaceuticals". Archived from the original on 22 August 2015. Retrieved 25 October 2015.
- ^ a b Edney A, Colbey L (17 November 2015). "The Female Libido Pill Is No Viagra". Bloomberg Business. Archived from the original on 17 November 2015. Retrieved 18 November 2015.
- ^ "Addyi Flibanserin". GoodRx. Archived from the original on 29 January 2021. Retrieved 26 September 2019.
Further reading
[edit]- Dean L (September 2019). "Flibanserin Therapy and CYP2C19 Genotype". In Pratt VM, McLeod HL, Rubinstein WS, Scott SA, Dean LC, Kattman BL, et al. (eds.). Medical Genetics Summaries. National Center for Biotechnology Information (NCBI). PMID 31550099. Archived from the original on 26 October 2020. Retrieved 15 April 2020.
- Aubert Y (December 2012). Sex, aggression and pair-bond: a study on the serotonergic regulation of female sexual function in the marmoset monkey (Thesis). Leiden University. hdl:1887/20268. ISBN 978-94-6182-195-9.
- Marazziti D, Palego L, Giromella A, Mazzoni MR, Borsini F, Mayer N, et al. (June 2002). "Region-dependent effects of flibanserin and buspirone on adenylyl cyclase activity in the human brain". The International Journal of Neuropsychopharmacology. 5 (2): 131–140. doi:10.1017/S1461145702002869. PMID 12135537.
- Podhorna J, Brown RE (June 2000). "Flibanserin has anxiolytic effects without locomotor side effects in the infant rat ultrasonic vocalization model of anxiety". British Journal of Pharmacology. 130 (4): 739–746. doi:10.1038/sj.bjp.0703364. PMC 1572126. PMID 10864879.
- Brambilla A, Baschirotto A, Grippa N, Borsini F (December 1999). "Effect of flibanserin (BIMT 17), fluoxetine, 8-OH-DPAT and buspirone on serotonin synthesis in rat brain". European Neuropsychopharmacology. 10 (1): 63–67. doi:10.1016/S0924-977X(99)00056-5. PMID 10647099. S2CID 1470166.
External links
[edit]- "The Company Behind 'Female Viagra' Just Raised $20 Million in Funding". Fortune. 4 September 2019.
- "The Women's Libido Pill Is Back, and So Is the Controversy". Bloomberg. 13 June 2018.
Flibanserin
View on GrokipediaFlibanserin (trade name Addyi) is a nonhormonal medication approved by the U.S. Food and Drug Administration (FDA) in 2015 as the first pharmacologic treatment for acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women and postmenopausal women under 65 years of age without co-existing medical or psychiatric conditions, medication effects, or relationship problems contributing to low libido.[1][2][3] Originally developed as an antidepressant in the 1990s, flibanserin failed to demonstrate efficacy for depression but showed signals of enhancing sexual function in early trials.[2] It is administered orally as a 100 mg tablet taken once daily at bedtime, with discontinuation recommended if no improvement occurs after eight weeks.[1] Flibanserin acts centrally in the brain as a postsynaptic 5-HT1A receptor agonist and 5-HT2A receptor antagonist, with additional binding at other serotonin, dopamine, and norepinephrine receptors, though its precise mechanism for increasing sexual desire remains unknown.[4][2] Pivotal phase III clinical trials demonstrated modest efficacy, with mean increases in satisfying sexual events (SSEs) of approximately 0.5 to 1.0 per month over placebo and small improvements in Female Sexual Function Index (FSFI) desire domain scores, alongside reductions in distress associated with low desire.[5][6] However, benefits were inconsistent across studies, and the drug's effect size has been characterized as clinically marginal by some analyses.[7] The drug's path to approval was marked by significant controversy, including two prior FDA rejections in 2010 and 2013 due to an unfavorable benefit-risk profile stemming from limited efficacy relative to side effects such as dizziness, somnolence, nausea, fatigue, and hypotension—particularly severe when combined with alcohol, leading to a boxed warning and restricted distribution program.[1][8] Approval followed an advocacy campaign by pharmaceutical interests and women's groups alleging FDA gender bias, contrasted against critiques that the decision prioritized commercial pressures over rigorous evidence standards, as the agency had approved no analogous treatments for male sexual dysfunction despite extensive submissions.[9][10] Post-approval, real-world utilization has remained low, reflecting ongoing debates about its net clinical value.[11]
Medical Uses
Indications and Patient Selection
Flibanserin is indicated for the treatment of acquired, generalized hypoactive sexual desire disorder (HSDD) in premenopausal women, as approved by the U.S. Food and Drug Administration (FDA) on August 18, 2015.[1][12] On December 15, 2025, the FDA expanded the indication to include postmenopausal women under 65 years old.[13] HSDD in this context is defined as a persistent deficiency in sexual fantasies and desire for sexual activity that causes marked distress or interpersonal difficulty, is not better explained by another mental disorder, and is not attributable to the effects of a substance or medical condition.[2] The approval specifies that the condition must be generalized (not limited to certain situations or partners) and acquired (developed after a period of normal sexual function), excluding lifelong cases.[1] Flibanserin is suitable only for HSDD not attributable to medical, psychiatric, or relational factors and is not indicated for enhancing arousal, lubrication, or orgasm.[1] Patient selection requires confirmation that low sexual desire is not due to co-existing medical, psychiatric, or relationship issues; medications or substances affecting libido; or other reversible causes, such as hormonal imbalances or untreated depression.[2][14] A thorough clinical evaluation, including medical history, physical examination, and exclusion of alternative etiologies via laboratory tests if indicated, is essential prior to initiation.[15] Flibanserin is not indicated for men, cases of situational HSDD, or postmenopausal women aged 65 years and older, and treatment should be discontinued if no improvement in HSDD symptoms occurs after 8 weeks.[1][9][13]Dosage and Administration
Flibanserin is administered orally as a 100 mg tablet once daily at bedtime.[1] This timing reduces the risks of hypotension, syncope, accidental injury, and central nervous system depression—such as somnolence and sedation—that are more likely during waking hours.[1] The medication may be taken with or without food, though ingestion with food increases systemic exposure (AUC) by 1.18- to 1.56-fold and prolongs the time to maximum concentration (Tmax) to 0.9-1.8 hours.[1] Dose adjustments are not recommended; however, flibanserin is contraindicated in patients taking moderate or strong CYP3A4 inhibitors due to elevated flibanserin concentrations that heighten risks of severe hypotension and syncope.[1] If initiating flibanserin after discontinuing such an inhibitor, treatment should begin at least 2 weeks after the last dose of the inhibitor.[1] It is also contraindicated in hepatic impairment for similar pharmacokinetic reasons.[1] Alcohol use is contraindicated owing to increased risk of severe hypotension and syncope; patients should avoid alcohol entirely, or if consuming 1-2 standard drinks, wait at least 2 hours before bedtime dosing, while skipping the dose if 3 or more drinks are consumed that evening.[1][16] In case of a missed dose, the next scheduled dose should be taken at bedtime without doubling up.[16] Treatment discontinuation is advised if no improvement in hypoactive sexual desire disorder symptoms occurs after 8 weeks.[1]Pharmacology
Chemical Properties and Structure
Flibanserin is a synthetic small molecule classified within the phenylpiperazine chemical class, featuring a central benzimidazol-2(1H)-one core substituted at the nitrogen position with a 2-(piperazin-1-yl)ethyl chain, where the distal piperazine nitrogen is attached to a 3-(trifluoromethyl)phenyl moiety.[17] This structure confers lipophilic character suitable for central nervous system penetration.[17] The IUPAC name for flibanserin is 1-[2-[4-[3-(trifluoromethyl)phenyl]piperazin-1-yl]ethyl]-1,3-dihydro-2H-benzimidazol-2-one, with the CAS registry number 167933-07-5.[17] Its molecular formula is C₂₀H₂₁F₃N₄O, and the molecular weight is 390.4 g/mol.[17] [18] Physicochemical properties include a solid state at room temperature, low water solubility of approximately 0.178 mg/mL, and an octanol-water partition coefficient (logP) ranging from 3.32 to 3.83, indicating moderate lipophilicity.[17] The compound exhibits pKa values of 12.91 (acidic) and 7.03 (basic), reflecting the benzimidazolone and piperazine functionalities, respectively.[17]Mechanism of Action
Flibanserin exerts its effects primarily through modulation of serotonin receptors in the central nervous system, functioning as a postsynaptic 5-HT1A receptor agonist and a 5-HT2A receptor antagonist.[2] This profile distinguishes it from traditional antidepressants, as it preferentially targets these receptors at clinically relevant doses to alter monoamine neurotransmission without broadly inhibiting serotonin reuptake.[19] Secondary interactions include weaker antagonism at 5-HT2B, 5-HT2C, and dopamine D4 receptors, though these contribute less to its primary therapeutic action.[17] The receptor agonism at 5-HT1A sites and antagonism at 5-HT2A sites results in increased extracellular levels of dopamine and norepinephrine, alongside reduced serotonin activity, particularly in the prefrontal cortex—a region implicated in executive function, motivation, and reward processing.[2] This neurotransmitter rebalancing is hypothesized to counteract inhibitory serotonergic influences on sexual desire pathways, enhancing excitatory signaling from dopamine and norepinephrine without elevating dopamine in the nucleus accumbens, thereby minimizing abuse potential.[19] In vivo studies demonstrate regional selectivity, with transient decreases in serotonin observed in the prefrontal cortex, nucleus accumbens, and hypothalamus, supporting a mechanism that promotes pro-sexual motivational states over generalized mood elevation.[17]Pharmacokinetics and Metabolism
Flibanserin is administered orally with an absolute bioavailability of 33%.[1] [2] Following a single 100 mg dose, the mean maximum plasma concentration (Cmax) is approximately 419 ng/mL, achieved at a median time (Tmax) of 0.75 hours (range: 0.75–4 hours).[1] Ingestion with food, particularly high-fat meals, increases the area under the curve (AUC) by 1.18- to 1.56-fold and delays Tmax, though steady-state pharmacokinetics remain similar regardless of food intake.[1] The drug exhibits high plasma protein binding of approximately 98%, primarily to albumin.[1] [17] Volume of distribution data is not well-characterized in available sources. Flibanserin undergoes extensive hepatic metabolism, primarily via cytochrome P450 enzyme CYP3A4 and to a lesser extent CYP2C19, with minor contributions from CYP1A2, CYP2B6, CYP2C8, CYP2C9, and CYP2D6.[1] [2] [17] This process yields at least 35 metabolites, most in low plasma concentrations; two pharmacologically inactive metabolites—6,21-dihydroxy-flibanserin-6,21-disulfate and 6-hydroxy-flibanserin-6-sulfate—achieve concentrations comparable to the parent compound.[1] [17] CYP3A4 inhibitors (e.g., ketoconazole) can increase exposure up to 7-fold, while inducers (e.g., rifampin) reduce it by 95%; CYP2C19 poor metabolizers experience a 1.3-fold increase in exposure.[1] Elimination occurs predominantly through feces (51%) and urine (44%), with the parent drug undetectable in excreta due to extensive metabolism.[1] [17] The terminal elimination half-life is approximately 11 hours.[1] [2] Pharmacokinetics are minimally altered in mild to moderate renal impairment (AUC increase of 1.1- to 1.2-fold) but significantly prolonged in hepatic impairment (AUC increase up to 4.5-fold), contraindicating use in the latter.[1] [2] Alcohol does not significantly affect pharmacokinetic parameters, though it exacerbates pharmacodynamic risks such as hypotension.[1]Clinical Efficacy
Pivotal Clinical Trials
The pivotal clinical trials supporting flibanserin approval consisted of three randomized, double-blind, placebo-controlled phase 3 studies (coded as 511.71, 511.75, and 511.147, also known as DAISY, VIOLET, and BEGONIA, respectively) conducted in North American premenopausal women aged 18-45 with acquired, generalized hypoactive sexual desire disorder (HSDD) of at least six months' duration.[20] These trials enrolled a total of approximately 2,375 participants, excluding those with other sexual dysfunctions, depression, or use of serotonergic medications, and required stable relationships and no recent hormonal contraceptive changes.[20] Participants received flibanserin 100 mg once daily at bedtime or placebo for 24 weeks, with primary co-endpoints of change from baseline in monthly satisfying sexual events (SSEs, recorded via daily e-diary) and either eDiary sexual desire score (studies 511.71 and 511.75) or Female Sexual Function Index (FSFI) desire domain score (study 511.147).[20] [21] Across the trials, flibanserin demonstrated statistically significant but modest efficacy. In study 511.71 (n=570), the median increase in SSEs was 1.0 more per month with flibanserin than placebo (p<0.01), with a 0.4-point greater improvement in eDiary desire score (p<0.001).[20] Study 511.75 (n=737) showed a 0.5 SSE increase over placebo (p<0.0001) and 0.3-point desire improvement (p<0.05).[20] In study 511.147/BEGONIA (n=1,068), flibanserin yielded a 1.0 SSE increase versus placebo (from baseline means of 2.5 vs. 1.5 events per 28 days; p≤0.0001) and 0.3-point FSFI desire gain (p<0.0001), alongside reductions in Female Sexual Distress Scale-Revised (FSDS-R) distress scores.[20] [21] Pooled analyses confirmed consistency, with flibanserin increasing SSEs by 0.5-1.0 events/month over placebo and improving desire by 0.3-0.4 points, though absolute changes from low baselines remained small (e.g., SSE totals around 3-4/month).[22] Secondary outcomes, including FSFI total scores and patient-reported benefit, also favored flibanserin, with odds ratios for response 2.0-2.4 times higher than placebo.[23]| Trial (Code) | Participants (Flibanserin/Placebo) | SSE Change Over Placebo (per 28 days) | Desire Score Change Over Placebo | Key p-values |
|---|---|---|---|---|
| 511.71 (DAISY) | 280/290 | +1.0 (median) | +0.4 (eDiary) | SSE: <0.01; Desire: <0.001 |
| 511.75 (VIOLET) | 365/372 | +0.5 (median) | +0.3 (eDiary) | SSE: <0.0001; Desire: <0.05 |
| 511.147 (BEGONIA) | 532/536 | +1.0 (mean diff.) | +0.3 (FSFI domain) | SSE: ≤0.0001; Desire: <0.0001 |
Long-Term Studies and Real-World Data
A 52-week open-label extension study (SUNFLOWER) enrolled women with hypoactive sexual desire disorder (HSDD) who had completed prior randomized controlled trials of flibanserin or placebo; participants received flexible dosing of 50 mg or 100 mg once daily at bedtime.[24] Sexual function, as measured by the Female Sexual Function Index (FSFI), improved among participants, with the proportion of baseline FSFI remitters maintaining remission rising to approximately 90% by week 4 and stabilizing thereafter.[25] Flibanserin was generally well tolerated, with 1.2% of participants experiencing serious adverse events and 10.7% discontinuing due to any adverse events over the 52 weeks.[11] A separate 28-week open-label safety study included pre- and postmenopausal women with HSDD who had finished preceding flibanserin trials, aiming to assess extended tolerability and preliminary efficacy signals.[26] Adverse events aligned with shorter-term data, including somnolence, dizziness, and nausea, but no new long-term risks emerged beyond those observed in phase 3 trials.[27] However, these open-label designs lack placebo controls, limiting causal inferences about sustained efficacy versus natural remission or placebo effects.[28] Real-world post-approval data on flibanserin remain limited, with no large-scale observational studies quantifying long-term adherence or outcomes in routine clinical practice.[29] Post-marketing pharmacovigilance has focused on safety, including required studies on alcohol interactions that prompted the FDA in 2019 to relax prior restrictions, finding hypotension and syncope risks lower than pre-approval models suggested when alcohol is limited to moderate intake.[30] Small survey-based explorations indicate variable patient-reported benefits in sexual desire, but high discontinuation rates due to side effects mirror trial findings, underscoring modest net clinical utility.[31] Ongoing monitoring is emphasized, as chronic daily use over years could reveal risks not captured in extensions up to one year.[32]Comparative Effectiveness
Flibanserin exhibits modest efficacy relative to placebo in premenopausal women with acquired, generalized hypoactive sexual desire disorder (HSDD), as evidenced by pooled analyses of three pivotal randomized controlled trials. The drug at 100 mg daily dosing increased satisfying sexual events (SSEs) by a mean of 0.49 events per month compared to placebo (95% CI, 0.32-0.67), alongside improvements in Female Sexual Function Index desire domain scores with effect sizes of 0.29-0.44 and decreased distress with effect sizes of 0.24-0.44.[33][34] These gains typically emerge after 4-8 weeks of continuous use but remain small in absolute terms, with approximately 10-20% of treated women achieving clinically meaningful responses versus placebo.[35] High placebo response rates in HSDD trials—often exceeding 30% for desire improvements—contribute to the limited incremental benefit observed.[36] No head-to-head randomized trials compare flibanserin directly to other U.S. FDA-approved pharmacotherapies for HSDD, such as bremelanotide (Vyleesi), an on-demand melanocortin receptor agonist approved in 2019 for premenopausal women. Indirect comparisons from separate placebo-controlled studies suggest overlapping modest profiles: flibanserin yields roughly one additional SSE every two months over placebo, while bremelanotide shows no net increase in SSEs but marginal gains in desire scores (effect size ~0.2-0.3).[37][38] Flibanserin's daily oral regimen contrasts with bremelanotide's subcutaneous self-injection as needed, potentially favoring the latter for convenience despite comparable efficacy limitations. Off-label alternatives like sildenafil demonstrate inconsistent benefits for desire (versus arousal) in women and lack robust evidence superior to flibanserin.[39] For postmenopausal women, where flibanserin lacks FDA approval, transdermal testosterone therapy—administered via patches or gels—has shown consistent desire improvements in meta-analyses of randomized trials, with effect sizes often exceeding those of flibanserin in premenopausal cohorts (e.g., standardized mean differences of 0.4-0.6 for sexual function domains).[40][41] Testosterone's hormonal mechanism addresses androgen deficiencies linked to menopause, whereas flibanserin's serotonergic modulation yields smaller postmenopausal effects in exploratory trials like SNOWDROP and PLUMERIA (SSE increase ~0.3-0.5/month over placebo).[42] Nonpharmacological options, including cognitive behavioral therapy and mindfulness-based interventions, report larger effect sizes (d > 0.5) for HSDD symptoms, outperforming flibanserin in cross-trial benchmarks, though direct comparisons remain scarce.[36] Overall, flibanerin's benefits appear incremental and patient-specific, with effect sizes akin to antidepressants for mood disorders but debated for clinical meaningfulness given adverse effect burdens.[43]Safety Profile
Common Adverse Effects
The most common adverse reactions to flibanserin in three 24-week, randomized, double-blind, placebo-controlled phase 3 clinical trials (pooled n=2,375 premenopausal women with acquired, generalized hypoactive sexual desire disorder) were those occurring at an incidence of at least 2% and exceeding placebo rates: dizziness, somnolence, nausea, fatigue, insomnia, and dry mouth.[1] [44] These central nervous system-related effects align with flibansterin's mixed serotonin receptor agonism and antagonism, contributing to sedative-like properties, though the drug's bedtime dosing recommendation aims to mitigate daytime impairment.[1]| Adverse Reaction | Flibanserin Incidence | Placebo Incidence |
|---|---|---|
| Dizziness | 11.4% | 2.2% |
| Somnolence | 11.2% | 3.1% |
| Nausea | ~10% | ~5% |
| Fatigue | ~9% | ~5% |
| Insomnia | 5.0% | 3.0% |
| Dry mouth | 2.0% | 1.0% |
Serious Risks and Contraindications
Flibanserin is associated with a boxed warning highlighting the risk of severe hypotension and syncope, which can occur due to central nervous system (CNS) and vascular effects, particularly when combined with alcohol or in the presence of pharmacokinetic interactions that elevate drug concentrations. These events may lead to accidental injury or falls, with clinical trials reporting syncope rates of up to 0.4% in treated patients versus 0% in placebo groups, though post-marketing surveillance has documented additional cases.[16][2] Concomitant use with alcohol, while not an absolute contraindication following a 2019 FDA label update based on safety data from over 8,000 patients showing low incidence of severe events with limited intake, still substantially increases hypotension and syncope risk if consumed close to dosing; patients are instructed to wait at least 2 hours after 1 or 2 standard drinks before bedtime administration or skip the dose if more alcohol is consumed that evening.[16][46][47] Contraindications include:- Hepatic impairment (any degree), as it markedly elevates flibanserin exposure (AUC increase of 3- to 6-fold in mild cases), amplifying hypotension and syncope risks.[16]
- Concurrent use with moderate or strong CYP3A4 inhibitors (e.g., ketoconazole, fluconazole, ritonavir), which can increase flibanserin levels by over 2-fold, leading to severe adverse events.[16][2]