Questions remain about the sexual side effects of Merck’s baldness drug Propecia. A review published in the Journal of the American Medical Association (JAMA) Dermatology analyzed 34 clinical trials and found that none of them sufficiently reported on this risk. The study was conducted by researchers at Northwestern University, who said the findings raise concerns about the drug’s safety.
The main active ingredient in Propecia is finasteride. Merck’s Proscar, which is used to treat an enlarged prostate, also contains finasteride but in higher concentrations.
The drug label warns of the risk of decreased sex drive, impotence and problems with ejaculation, but the JAMA review says these side effects have not been adequately studied.
“Not one of the 34 published clinical trial reports provided adequate information about the severity, frequency or reversibility of sexual adverse effects,” the study states.
Researchers said the lack of data leaves key questions unanswered, such as the how long the side effects may persist and whether or not they are permanent. 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.
Steven Belknap, lead author and research assistant professor of dermatology
Steven Belknap, lead author and research assistant professor of dermatology and general internal medicine at Northwestern University Feinberg School of Medicine, said “People who take or prescribe the drug assume it’s safe, but there is insufficient information to make that judgment,”
He said the studies did not give adequate 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 stems from a meta-analysis involving 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.”