A review published in the Journal of the American Medical Association (JAMA) Dermatology highlights lingering questions about the sexual side effects of Propecia and Proscar. Researchers at Northwestern University looked at 34 clinical trial of patients taking finasteride (the main active ingredient in both drugs) and found that none adequately reported on sexual side effects.
Merck’s Propecia and Proscar both contain finasteride as the main active ingredient, but at different strengths. Propecia contains a smaller dose and is marketed to treat male pattern baldness while Proscar is used to treat an enlarged prostate. The drug label warns of the risk of decreased sex drive, impotence and problems with ejaculation. The JAMA review, however, says that research into these side effects is insufficient. “Not one of the 34 published clinical trial reports provided adequate information about the severity, frequency or reversibility of sexual adverse effects,” the authors state.
The study said that crucial questions remain unanswered, such as how long the side effects last and whether or not they are reversible. Most of the studies published were for patients who took finasteride for one year or less, but a third of men took it for longer than one year. “People who take or prescribe the drug assume it’s safe, but there is insufficient information to make that judgment,” said Steven Belknap, lead author and research assistant professor of dermatology and general internal medicine at Northwestern University Feinberg School of Medicine.
Belknap said there is not enough information about the severity or frequency of sexual side effects. “Was this information obtained but then not included in published articles? Or, were these clinical trials performed in a way that simply didn’t capture this essential information?” he asked. “And most importantly, is the risk to benefit ratio of finasteride acceptable?”
The review is based on a meta-analysis using data from over 5,700 men taking finasteride. Thomas Moore of the Institute for Safe Medication Practices in Alexandria, Virginia said in an accompanying editorial that there should be improved study of drugs’ potential risks and not just potential benefits. “The international standard for the duration of clinical testing for non–life-threatening diseases requires that only 300 patients be observed for one year or more, and not necessarily with a comparison group,” Moore wrote. “This standard is not adequate and should be reassessed.”