The prescription drug finasteride, marketed as Propecia and Proscar by Merck, may cause side effects like low libido and inability to orgasm in men who use the medication to battle hair loss, and those symptoms may persist even after stopping the drug, according to a new study to be published in the Journal of Sexual Medicine.
“Reversible” symptoms of sexual dysfunction are known side effects of finasteride — as is indicated on the drug’s label — but the new survey of 76 men aged 21 to 46 found that sexual problems including erectile dysfunction and premature ejaculation lasted at least three months after men stopped taking the pill. (More on Time.com: You May Be Less Bald Than You Think)
Lead researcher Dr. Michael Irwig of George Washington University’s medical school told AOL Health:
“Three months was the minimum, but some of these guys had sexual symptoms for years, some … for five to 10 years after. These were young guys with no medical problems, no psychiatric problems, who happened to develop these side effects.”
Among the study participants, some of whom had taken finasteride for just a few days, 94% said they experienced low sexual desire, 92% reported low sexual arousal, 92% developed erectile dysfunction and 69% had trouble having orgasm.
Participants had taken finasteride for 28 months on average, and reported sexual problems for an average 40 months, but the study author said that 10% of the surveyed men had used the drug for less than a month. (More on Time.com: Plastic Surgery Isn’t Just for Women Anymore)
The medication carries a warning about persistent sexual dysfunction, along with potential psychological problems, in the U.K. and Sweden. But U.S. labeling doesn’t contain such warnings.
“It’s obviously having some effect on the brain,” Irwig told AOL Health. “It’s messing up different hormonal pathways.”