Will this hair loss drug kill your sex drive?

None of the clinical trial reports of a drug to treat hair loss in men address erectile dysfunction and low sex drive side effects, says Steven Belknap. "People who take or prescribe the drug assume it's safe, but there is insufficient information to make that judgment." (Credit: Vox Efx/Flickr)

Men taking the hair loss drug finasteride have access to very little information about the drug’s sexual side effects, experts say. None of the 34 published reports from clinical trials offer information about erectile dysfunction and low sex drive.

The drug blocks 5α-reductase in the scalp and male reproductive organs, inhibiting the conversion of the male hormone testosterone to its more potent form, 5α-dihydrotestosterone (5α- DHT).

Men who take finasteride experience a 70 percent reduction in the amount of 5α-DHT in their blood.

How safe is it?

The published reports fail to provide adequate information about the severity, frequency, or reversibility of sexual adverse effects, and they fail to answer several key questions:

  • How safe is finasteride? Specifically, what is the risk that a man taking finasteride will develop sexual dysfunction?
  • How severe is finasteride-associated sexual dysfunction when it happens to a man?
  • If a man gets sexual dysfunction while taking finasteride, will sexual function return to normal when the drug is stopped? What is the risk of persistent sexual dysfunction associated with taking finasteride?

Is the risk acceptable?

Finasteride was originally developed to treat enlarged prostate (prostatic hyperplasia) in older men. Men who take the drug for male pattern hair loss are typically younger and take a dose of finasteride that is about one-fifth the dose used for prostatic hyperplasia.

“People who take or prescribe the drug assume it’s safe, but there is insufficient information to make that judgment,” says Steven Belknap, research assistant professor of dermatology and general internal medicine at Northwestern University Feinberg School of Medicine.

“Our findings raise several questions,” Belknap says. “Why do the published reports of these 34 clinical trials not provide adequate information about the severity and frequency of sexual toxicity? 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? And most importantly, is the risk to benefit ratio of finasteride acceptable?”

Published in JAMA Dermatology, the study is a report from the RADAR (Research on Adverse Drug Events and Reports) project at Northwestern’s Feinberg School. The RADAR study points to a larger problem in the way clinical trials are performed and analyzed in meta-analyses.


Typically, there is more focus on the desirable effects of the drug being studied compared to the toxic effects,” Belknap says.

Of 5,704 men in the Northwestern Medicine clinical data repository who were treated for male pattern baldness with finasteride, only 31 percent met inclusion criteria for the pivotal trials referenced in the manufacturer’s “Full Prescribing Information.”

Because of this, the available information from clinical trials doesn’t apply to most of the men who took finasteride for male pattern baldness. For example, some men with hair loss who are taking finasteride have diabetes mellitus, high blood pressure, or are taking other drugs such as diuretics or antidepressants that also increase the risk of sexual dysfunction.

Further, the duration of the drug safety evaluation was limited to one year or less for 26 of 34 trials (76 percent.) But 33 percent of men in the Northwestern clinical data repository took finasteride for more than a year.

The National Cancer Institute of the National Institutes of Health and the Post-Finasteride Syndrome Foundation funded the work.

Source: Northwestern University