Men who have taken a popular pill for baldness say they've experienced persistent sexual dysfunction for months, or even years, after stopping the drug.
The new study, published in the Journal of Sexual Medicine, found that men who take finasteride, sold under the brand names Propecia and Proscar, may develop an ongoing loss of libido and orgasm, even after they go off the medication.
In some cases, they could have other lasting sexual side effects, including premature ejaculation and erectile dysfunction, according to lead researcher Dr. Michael Irwig of George Washington University's medical school.
"It's obviously having some effect on the brain," Irwig told AOL Health. "It's messing up different hormonal pathways. Some of these pathways are important for things like libido and sexual function."
Finasteride, the most common hair-loss pill, has previously been linked to "reversible" sexual impairment, as noted on the drug's label, said Irwig. But "this is the first series to find that symptoms persisted for at least three months despite stopping finasteride," he added.
"Three months was the minimum, but some of these guys had sexual symptoms for years, some ... for five to 10 years after," he told AOL Health. "These were young guys with no medical problems, no psychiatric problems, who happened to develop these side effects."
Irwig and his team interviewed 71 men aged 21 to 46 who had taken Propecia or Proscar and reported new sexual side effects after they started the drugs. None of the participants had a history of sexual dysfunction or other conditions that might have contributed, Irwig said -- and some had only been on finasteride for a few days.
Ninety-four percent said they'd experienced low sexual desire, 92 percent reported a dip in sexual arousal and 69 percent had trouble with orgasm, according to the findings. Another 92 percent said they developed erectile dysfunction after taking finasteride.
On average, participants had been on the baldness drug for 28 months and had chronic sexual problems for an average of 40 months, the research showed.
But 10 percent of those studied had used finasteride for less than a month, Irwig told AOL Health.
"It's scary," he said. "For the lack of orgasm and libido, there is no treatment."
Other reported adverse side effects of finasteride are depression, suicidal thoughts and anxiety. Merck is currently fighting a number of lawsuits involving the drug, including one in Canada and another in Connecticut.
The company does not warn of possible psychological or persistent sexual problems in information about finasteride on its website, nor does it mention those symptoms on its U.S. labeling. Irwig said the drug does carry warning labels in the U.K. and Sweden about ongoing sexual impairment.
"Be aware that this is a potential sexual side effect," he cautioned. "If somebody chooses to take this medicine, there is that risk. They have to make the decision that it's a risk they're willing to take."
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