Credit: Photograph by The Voorhes

Go see your doctor about a receding hairline, and there's a good chance you'll walk away with a prescription for finasteride — better known by its brand name, Propecia. The FDA-approved pill, which came out in 1997, thickens hair in 65 percent of those who take it. More than 26 new generic versions, priced at less than a dollar a pill (versus $3 for Propecia), have made the drug even more attractive. While the packaging warns of a 1 to 2 percent chance of temporary sexual side effects, millions of men consider it a risk worth taking. But emerging research and a slew of lawsuits suggest that finasteride may be more dangerous than previously believed, with side effects — inability to orgasm, painful erections, chronic depression, insomnia, brain fog, and suicidal thoughts — that can last long after patients stop taking the pill.

"My yardstick for treating any patient is, what would I do if this were my own son?" says Dr. Nelson Novick, a clinical professor of dermatology at Mount Sinai School of Medicine in New York. "Ten years ago I would have answered differently, but now I would not feel comfortable recommending Propecia to a young, sexually active man."

Most dermatologists still prescribe finasteride, explaining that they rarely hear of persistent symptoms from patients. There could be a reason for that, researchers say. Men may have no idea that cognitive side effects would have anything to do with taking a hair-loss pill, particularly if those problems continue after they stop taking the drug. And many would be embarrassed to bring up sexual problems to a dermatologist or researcher, particularly a female. "Sexual impairment induced by antidepressant drugs was underestimated for decades for just this reason," wrote Thomas Moore, a researcher with the Institute for Safe Medication Practices, in an editorial in the June issue of JAMA Dermatology. Moore said side-effect estimates for those drugs have since jumped from between 1 and 3 percent to between 30 and 60 percent.


Since 2011, 1,245 lawsuits have been filed against Propecia's manufacturer, Merck, alleging that the company failed to warn users of a constellation of sexual and cognitive side effects — which patients and physicians call Post-Finasteride Syndrome (PFS) because, they say, symptoms often persist after discontinuing the drug. This spring, the National Institutes of Health added PFS to its rare-diseases database. And in March, a California woman filed the first wrongful death suit against Merck. Her husband, a 40-year-old IT executive and father of two with no history of mental illness, killed himself in March 2013. His family blames finasteride.

In a statement, Merck said the company "stands behind the demonstrated safety and efficacy profile of Propecia." In recent years, it also added depression and persistent sexual problems to its list of possible side effects, deep in the fine print. It intends to defend itself vigorously when the first cases go to court, likely in 2016. The company will undoubtedly argue that millions use Propecia without harm — sales hit $264 million in 2014 — and that serious problems are rare.

Not rare enough, says Steven Rossello, a 32-year-old who filed the first suit against Merck, in 2011. "There's a lot of talk about sexual side effects, but the worst effects are the mental ones," Rossello says. Despite stopping the drug in 2010, he says he suffered a finasteride-induced long-term depression that cost him his fiancée and job as an agent with the Department of Homeland Security.

Recent research suggests that finasteride can impact levels of neuro-protective, mood-regulating steroids in the brain, explains Dr. Michael Irwig, an associate professor of medicine at George Washington University whose research has linked its use to depression and suicidal tendencies. According to a review published in Pharmacotherapy: The Journal of Human Pharmacology and Drug Therapy in July, the FDA has received more than three dozen reports of suicidal tendencies among Propecia users. Most resulted in hospitalization, death, or disability.


"Patients and physicians have been falsely reassured," says Steven Belknap, an assistant professor of dermatology at Northwestern University. In a meta-analysis published in JAMA Dermatology in April, he reviewed the 34 clinical trials performed on finasteride and found that "none adequately assessed safety," and all underreported potential adverse effects. "It is stunning," says Belknap. "Here we are 18 years after the initial approval, and if someone were to ask me if this drug is safe, I would have to say, 'I don't know.' " Merck, in its statement, said it "conducted well-designed clinical trials."

Why do so many doctors still prescribe the drug? The research on its cognitive side effects is relatively new, and the number of patients reporting problems low, dermatologists say. "I don't hesitate to prescribe it to appropriate patients, but I do spend more time now counseling them about the risks," says Boulder, Colorado, dermatologist Jeanie Leddon.

Knowing the drug's origins might prompt some to shy away from it. Finasteride has its roots in the 1970s, when scientists discovered a rare group of men in the Dominican Republic who were born with ambiguous genitalia and often mistakenly raised as girls. These men possessed other unique traits: They never lost their hair or had prostate problems. This was because they failed to produce an enzyme that converts testosterone to dihydrotestosterone, or DHT. DHT is critical for fetal development of male genitals, but in adults it impairs hair growth. Enter Merck, which unveiled a compound — finasteride — that slashes DHT levels 70 percent. As Belknap puts it, the drug works by mimicking the sex-steroid profile of pseudohermaphrodites. Some former male users equate this to "chemical castration." To this day, health officials warn women not to even touch finasteride pills, because doing so could cause genital malformations in an unborn boy.

In 1992, drug companies rolled out a finasteride tablet to treat an enlarged prostate. It's still prescribed by urologists who contend that, in this case, avoiding serious health problems outweighs the risk. Propecia, however, is a different story. "This is cosmetic," stresses Belknap. "This is not a lifesaving drug." And one that may come with a steep price.