Study Reveals Surprising Results for Female Libido Pill

The first systemic review of the women's libido Tx flibanserin has been released
The first systemic review of the women's libido Tx flibanserin has been released

How effective and safe is flibanserin (Addyi; Valeant) for the treatment of hypoactive sexual desire disorder (HSDD) in women?  A new study published in JAMA Internal Medicine aimed to assess the clinical benefits of this new prescription drug which has stirred up controversy since even before its FDA approval back in August 2015. This is the first systematic review and meta-analysis to address the clinical impact of flibanserin in treating women with HSDD.

While the mechanism of action for flibanserin in the treatment of HSDD is unknown, it is thought to work by restoring prefrontal cortex control over the brain's motivation/rewards structures enabling sexual desire to manifest. Specifically, flibanserin increases dopamine and norepinephrine while transiently decreasing serotonin in the brain's prefrontal cortex, which may be accomplished by reduced glutamate transmission. In vitro, flibanserin has demonstrated high agonist activity at 5-HT1A receptors and antagonist activity at 5-HT2A receptors; it also has moderate antagonist activities at the 5-HT2B, 5-HT2C, and dopamine D4 receptors.

For this study, researchers included eight studies (five published, three unpublished) which included nearly 6000 women (both pre- and postmenopausal) with generalized acquired HSDD according to the Diagnostic and Statistical Manual of Mental Disorders (4th Edition, Text Revision); all studies were randomized, double-blind, placebo-controlled trials. Primary efficacy outcomes included the number of satisfying sexual events (SSEs), monthly sexual desire intensity (eDiary desire score), and Female Sexual Function Index desire domain (FSFI desire). In addition to these, five secondary efficacy outcomes (FSFI total score, Female Sexual Distress Scale-Revised Item 13 and total score, Patient's Global Impression of Improvement, Patient Benefit Evaluation) and safety outcomes (any adverse events, investigator-defined drug-related adverse events, adverse events leading to study discontinuation, severe/serious adverse events) were included in the analysis.

Results indicate that the impact of flibanserin in producing a meaningful change in women with HSDD was small; patient's global impression of improvement scores showed minimal improvement to no change. When comparing flibanserin 100mg to placebo, researchers found that the pooled mean difference in SSE change from baseline was 0.49 (95% CI, 0.32–0.67); this varied depending on whether the study was published (0.58 [95% CI, 0.37-0.80]) or unpublished  (0.31 [95% CI, 0.00-0.62]) and also when factoring in premenopausal women only (0.65 [95% CI, 0.38-0.92]). For eDiary desire score, which was only measured in premenopausal women, the mean difference in change from baseline was 1.63 (95% CI, 0.45–2.82); for FSFI desire it was 0.27 (95% CI, 0.17–0.38). A statistically significant difference was seen between flibanserin 100mg versus placebo in all primary and secondary outcomes.

With regards to side effects, the risk ratio for study discontinuation due to adverse events was 2.19 (95% CI, 1.50–3.20). Compared to placebo, the most common adverse events reported for flibanserin 100mg were dizziness (4.00 [95% CI, 2.56–6.27]), somnolence (3.97 [95% CI, 3.01-5.24]), nausea  (2.35 [95% CI, 1.85-2.98]), and fatigue (1.64 [95% CI, 1.27-2.13]); overall ratio for most common adverse events was 2.86 (95% CI, 2.32–3.52). For serious adverse events (ie, hypotension, syncope), the risk ratio did not differ between flibanserin and placebo.

On average, treatment with flibaserin resulted in 0.5 additional SSEs per month but also significantly increased the risk of adverse events such as dizziness, somnolence, nausea, and fatigue, which were reported as mild or moderate in intensity. These adverse events, as well as more serious ones such as hypotension and syncope, may also be exacerbated by concurrent alcohol intake and CYP3A4 inhibitors (ie, oral contraceptives, fluconazole), both addressed in the prescribing information for flibanserin. Previous research indicates that nearly 90% of U.S. physicians would prescribe a pharmacological agent for the treatment of HSDD over available nonpharmacological treatments, but the findings of this study show that clinicians should weigh the marginal benefits of flibanserin with the risk of possibly significant side effects.

Given that the study excluded women with a wide range of medication uses, diseases (including psychological disorders), and those not in stable, heterosexual relationships, it is unclear to what extent these findings represent typical women with HSDD. The researchers conclude that "before flibanserin can be recommended in guidelines and clinical practice, future studies should include women from diverse populations, particularly women with (a history of) somatic and psychological comorbidities, medication use, and surgical menopause."

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