The first ever prescription pill to boost women's libido has won the approval of US regulators. Addyi got the final nod from the Food and Drug Administration (FDA) on Tuesday after three 24-week trials showed it to offer an increase in sexual desire in premenopausal women, though the agency does warn of side effects that include low blood pressure and fainting.
The company behind the drug, North Carolina-based Sprout Pharmaceuticals, has sought to develop a medication to treat acquired, generalized hypoactive sexual desire disorder (HSDD). This condition is defined by an absence of sexual desire that brings about significant stress and interpersonal difficulties. Studies have shown it affects nearly one in 10 US women.
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Addyl (aka flibanserin) is a serotonin 1A receptor agonist and a serotonin 2A receptor antagonist, but the FDA says the precise mechanism that gives it libido-enhancing properties is not currently known. While the drug has been tested in more than 11,000 women, the all important FDA approval follows three 24-week studies involving around 2,400 women with HSDD. The women were aged 36 on average and had suffered from the condition for an average of five years.
In the four weeks leading up to treatment, the women were made to record the number of satisfying sexual events experienced, measure their sexual desire on a scale ranging from 1.2 to 6.0 and measure the stress resulting from HSDD on a scale of zero to four.
The Addyi treatment increased the average number of satisfying sexual events by between 0.5 and 1 per month, compared to placebo treatments. It also increased the sexual desire measurement by 0.3 to 0.4 and reduced the related distress score by 0.3 to 0.4.
The side effects reported through the study include both sleepiness and insomnia, nausea, fatigue and dry mouth. On the more serious side, it can also induce severe hypotension, or dangerously low blood pressure, and a loss of consciousness. These risks are heightened and the effects more dramatic when the drug is mixed with alcohol or certain medicines. To help reduce the risk of adverse events due to sleepiness and possible hypertension, the once-daily drug is to be taken at bedtime.
Due to the potential side effects, the FDA has approved the drug with a couple of caveats. Those prescribing Addyi must undergo training through the FDA's risk evaluation and mitigation strategy (REMS), advise patients of the risks of drinking alcohol when using the drug, and both must fill out a Patient-Provider Agreement Form. Furthermore, the drug will carry a boxed warning, the strongest warning required by the FDA that accompanies drugs with serious adverse reactions. The FDA also points out that Addyi hasn't been shown to enhance sexual performance.
Sprout plans to conduct additional studies to better define the safety of Addyi. The drug is expected to be available from October 17.