No. It is neither effective nor safe.
By Adriane Fugh-Berman, MD, and Alessandra Hirsch, MS
Dr Fugh-Berman is Associate Professor, Dept. of Pharmacology and Physiology, Georgetown University Medical Center, Washington, DC.
Ms Hirsch is a medical student at the University of Illinois Medical School, Chicago.
The world of women’s health saw a contentious, controversial, and politically charged drug approval process last year: that of flibanserin, a drug to treat low libido in premenopausal women. Is this pill “a milestone … a breakthrough,” as important as the birth control pill, as stated by Sally Greenberg, the executive director of the National Consumers League?1 Or is it rather “a mediocre aphrodisiac with scary side effects?”2 Women have voted on this question with their feet. In the first 10 weeks the drug was on the market, only 1841 prescriptions were sold.3
Physicians who care about data should join the many women who have stayed away from the drug despite the hype. In our opinion, flibanserin is not very effective, not very safe, and should not be prescribed.
A mixed serotonin receptor agonist/antagonist that also has weak partial agonist effects on dopamine levels, flibanserin’s precise mechanism of action is unknown. What is known is that flibanserin is, at best, minimally effective. A recent meta-analysis and systematic review of 8 trials of flibanserin in 5914 women indicates that “sexually satisfying events” (which need include neither partner nor orgasm) increased by less than one-half event per month over placebo.4 While half an event a month might be worthwhile for a woman having no events, women in the clinical trials were not starting at zero; they were already having 2–3 sexually satisfying events per month at baseline.5 One trial participant was having 34 sexually satisfying events per month.6
Company-sponsored key opinion leaders downplay the importance of sexually satisfying events, suggesting that even if women are enjoying sex, they still “want to want.” This shows a misunderstanding of women’s sexuality. Many women have responsive rather than spontaneous desire; ie, desire follows arousal. Recognition of this entirely normal state is why hypoactive sexual desire disorder (HSDD), the condition flibanserin was approved to treat, is no longer in the Diagnostic and Statistical Manual of Mental Disorders (DSM), published by the American Psychiatric Association; it’s been replaced with female sexual interest/arousal disorder (FSI/AD). Lack of receptivity to sexual initiation or arousal in response to appropriate stimuli is necessary for diagnosis.7
Compared to placebo groups, only 9%–15% more subjects in the flibanserin group experienced any improvement in libido at all.8 It is unclear whether flibanserin actually has any specific effect on libido. The drug is highly sedating and sedation may increase receptivity, not to mention alter recall of events. Also, sleeping better can improve one’s sex life. While such paltry benefits might be acceptable in a risk-free drug, flibanserin can cause serious adverse effects, including unpredictable hypotension and sudden, prolonged unconsciousness. These events are not limited to the first dose—or even the first few weeks8—and there is no evidence that women become tolerant to the drug’s adverse effects.
Besides sudden prolonged unconsciousness and severe hypotension, flibanserin causes dizziness, somnolence, nausea, and fatigue. One in 5 subjects (21%) in clinical trials experienced symptoms consistent with CNS depression. Accidental injuries associated with CNS depression occurred more than twice as often in flibanserin-treated patients as in placebo-treated patients.8