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Female Viagra Doesn't Improve Sexual Desire

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After much review and public controversy, the FDA met this week and determined that flibanserin, a new medication that was hoped to be an effective treatment for female sexual arousal disorder, did not significantly improve symptoms of the disorder, and ruled against approving the medication.

Female sexual arousal disorder, also known as hypoactive sexual desire disorder, (HSDD) is a relatively new diagnosis. It was historically known as frigidity, and more attention was given to the concept of the lack of sexual desire or arousal as a biological disorder potentially treatable with pharmaceuticals. When Sildenifil (Viagra) appeared on the market with enormous publicity and profit for the pharmaceutical industry, a lack of desire in women came under consideration as a potentially treatable disease.

Possible causes may include stress, relationship problems, anger, or a lack of intimacy with sex partners.  There are also known medical causes including side effects of certain medications including some antidepressants, blood pressure medications, and birth control pills. Menopause may also decrease sexual arousal and stimulation, as well as depression.

Several potential treatments have been evaluated in the past. Low-dose testosterone showed some promise in women who have had a hysterectomy and oophorectomy (surgical removal of both the uterus and ovaries.) Several other potential medications have been evaluated but showed minimal benefit. Trials with a clitoral vacuum pump have been less successful than hoped for.

Flibanserin was first developed as a potential fast-acting antidepressant, but was found to be ineffective at treating depression. However, during drug trials, it was noted that the compound appeared to improve symptoms of sexual dysfunction in female participants.

While the biochemical pathways that lead to sexual desire and arousal are not fully defined, prior research suggests that dopamine and norepinephrine act as stimulators of sexual desire, and that serotonin inhibits sexual desire. Flibanserin may work by restoring a balance between these chemicals.

The data from several large-scale trials were presented in November of 2009. More than 5,000 premenopausal women with HSDD were studied in a placebo-controlled trial. Study participants took a 100-mg dose every night until the study was stopped. The women on flibanserin reported that on average they experienced an increase in sexually satisfying events from 2.8 to 4.5 times a month. The women perceived a significantly increased meaningful benefit.

However, the women on placebo also perceived a significant benefit and satisfying events rose for them as well, from 2.7 times a month to 3.7. 

Unfortunately the drug only produced a minimal increase in sexual desire in both groups of women.

Commonly reported side effects included dizziness, nausea, fatigue, somnolence, and insomnia.  Appendicitis was the most severe possible side effect, and was seen at slightly higher rates in those on the medication.

The manufacturers of flibanserin, Boeringer Ingelheim, presented their data to the FDA for approval last week, and the FDA declined to approve the drug at this time, but gave encouragement to keep working on the problem.

Reasons the FDA gave for disapproval included the relatively low rate of effectiveness on increasing satisfactory encounters, the minimal effect on increasing sexual desire, and the risk of side effects.