Thursday, March 11, 2010

Flibanserin: A Sex Pill for Woman?

Medications like Viagra, Levitra, and Cialis have revolutionized the male sexual health world, and brought the subject of sex “out of the closet”, for open discussion in the doctor’s office, but also in the media. Commercials for erections are everywhere. The “male pill” has certainly enabled many older men, or men with vascular conditions or injury to regain some sexual potency. Once it debuted in 1998, sex researchers were busily trying to adapt Viagra to women to see if it would help similarly. It does not. It can lead to engorgement of the clitoris, perhaps helping arousal, but it does not help achieve orgasm, increase desire, or decrease sexual pain.

In women, more often than not, desire must precede arousal (though the reverse is true), in order to become romantic. Many things can kill sexual desire: stress, fatigue, bad relationships, menopause, surgery, and many health conditions and the medications taken to treat them, whether physical or psychological. No less important, the loss of sexual desire must be bothersome. For example, if a woman has no sexual desire AND does want to have sex, then her low desire is NOT a problem. It must lead to distress in order to merit treatment of course. So is there help for improving women’s desire on the horizon? Is there a magic pill for women?

Actually, there are medications already on the market that improve sexual desire in women already. I will address testosterone supplementation, which is widely used to restore female libido, in a future post. It is effective and usually given in post-menopausal women, but must be monitored closely with blood tests, and there are risks with hormone replacement, and of course its use is still off-label in the US. Therefore, is there something coming down the pike to help low sexual desire in women?

This past November 2009 a huge pooled phase III study was presented at a sexual conference in Europe. Flibanserin, is still investigational, but may be approved by the FDA within a year or two. In multiple large studies conducted throughout the US and Europe, Flibanserin was shown, if taken once a bedtime, to significantly increased the number of satisfying sexual events and sexual desire, while significantly decreasing distress associated with Hypoactive Sexual Desire in pre-menopausal women. This is incredibly promising and has sex researchers very “excited” about it. It is a novel compound, unlike any other med out there and it is not a hormone.

Is it safe? Most adverse reactions to Flibanserin were mild to moderate. The dose that worked the best with tolerable side effects was 100 mg prior to bedtime. Most side effects were seen within the first 14 days. The pill therefore must be taken daily, as it was studied, in order to achieve its “desired” result of increased sexual desire. We do not know if it can be taken on an as needed basis, like Viagra. The most common side effects included: dizziness, nausea, fatigue, sleepiness and insomnia. They occurred in approximately 15% across all studies, and lead to discontinuation of treatment in those women.

So, how does it work? Flibanserin acts as an agonist and binds to the serotonin 5-HT1A receptor, and an antagonist at the 5 HT2A receptor, in certain brain regions. It acts as a neurotransmitter in the sexual response cycle, and is believed to restore the balance between inhibitory and excitatory factors leading to a better sexual response.

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