As finasteride use by younger men soars, some doctors caution about rare side effects

More young men are taking a medication to prevent hair loss, prompting some concerns that the oral drug has been linked to rare but potentially long-lasting side effects.

A report by Epic Research, conducted on behalf of NBC News, found that the number of men in the U.S. with finasteride prescriptions increased nearly 200% in the last seven years.

“It’s like water in my clinic,” said dermatologist Dr. Jerry Shapiro of NYU Langone Health. “I’m prescribing it all the time.”

While the Epic report looked at men 25 and older, Shapiro and other doctors say they are also seeing more young men seeking treatment at an earlier age, including some in their late teens looking to stop hair loss before it starts or gets worse.

Part of the rise in prescriptions could be linked to telemedicine companies such as Hims, Keeps and Ro that promote the drug on billboards and online ads, said Dr. Maria Colavincenzo, an associate professor of dermatology at Northwestern Feinberg School of Medicine, who has been in practice for a decade.

Social media influencers promote finasteride with videos about their hair loss and regrowth while taking the drug. Finasteride is also heavily touted on a popular Reddit community called tressless.

“People are interested in treating it a little bit younger than what I saw before,” said Colavincenzo.

Doctors say the daily pill is safe, although once someone starts taking it, they’ll need to continue for as long as they want to avoid hair loss. And there’s some controversy about the drug, due to the possibility of impotence that could last even after stopping the medication.

What is finasteride? Does it work?

Originally developed to treat an enlarged prostate, finasteride, also known by the brand name Propecia, has been approved by the Food and Drug Administration for hair loss for nearly 30 years.

It’s a daily pill that slows androgenetic alopecia, commonly referred to as male-pattern baldness. About half of men are affected by this kind of hair loss by age 50.

While there’s no definitive evidence that men who start the drug before they start losing their hair won’t ever go bald, doctors say the risk seems to be lower.

In this form of hair loss — characterized by a receding hairline and thinning at the back of the head — there are two main changes to the hair follicle that happen, according to Colavincenzo.

These include miniaturization, or the shrinking of hair follicles, and a slowing of the growth cycle of the hair, both of which lead to a decrease in the thickness of hair.

Finasteride blocks the 5-alpha reductase enzyme, preventing the conversion of testosterone to dihydrotestosterone (DHT) and reducing the levels of DHT in the body. DHT is the main hormone responsible for facial and body hair. On the flip side, high levels of DHT are believed to shrink hair follicles on the scalp and shorten the hair growth cycle, resulting in hair loss.

“If you block that signal telling the hair to shrink, then the hair doesn’t shrink, and it might even unshrink a little bit,” she said. “That’s how finasteride works.”

Why some people have high levels of DHT but will never go bald boils down to genetics, she said, and it’s an active area of research today.

Fortunately, it appears that a majority of men who take finasteride will have success in slowing down their hair loss.

Studies have shown the drug has a roughly 80% to 90% chance of preventing further hair loss, said Shapiro, who added that because the drug works better at prevention, the earlier you start the better. Once you start, however, it becomes a lifelong medication.

“Most things in medicine are lifelong,” said Shapiro, who is also a medical adviser to Keeps, which sells the drug online. “If you have high cholesterol you have to be on medication forever, or if you have high blood pressure you have to be on medication forever.”

Dr. Carolyn Goh, a dermatologist at UCLA Health, said that while long-term data on the drug’s efficacy is limited, data shows that the drug’s benefits are maintained over time. A recent study from researchers in Korea published in the Journal of Dermatology found that nearly 100% of men had the same or more hair than before they took the drug in a five-year follow-up.

“It’s very effective,” she said. “Although the response may be just keeping the hair from getting worse rather than necessarily growing hair, it works quite well.”

A separate study from researchers in Italy followed over 100 patients on finasteride for 10 years and found that 86% of men had no change to their hair.

While finasteride is extremely effective at preventing further hair loss, it’s not as good at regrowing hair that is already lost. This is why it’s often combined with minoxidil, a topical drug that is applied directly to the scalp to stimulate hair growth.

Colavincenzo said that some patients whom she’s followed for roughly a decade have had success with the drug, although they can’t always tell whether it’s doing the job.

“The hard thing is you often don’t know how well it’s working,” she said. “Even if your hair is just not getting worse it’s a success.”

Because male-pattern baldness is considered a cosmetic disorder, finasteride is not typically covered by insurance. It’s been available as a generic since 2006 and typically costs less than $100 per month.

What are finasteride side effects?

In 2022, after a patient advocacy group urged the FDA to take it off the market, the agency required prescription labels to warn of possible suicidal behavior in men taking the drug.

More recently, a 2023 article in the International Journal of Impotence Research, has fueled online debate over a phenomenon known as post-finasteride syndrome. The syndrome is linked to decreased libido, erectile dysfunction or even cognitive difficulties.

The most commonly reported side effects with finasteride include decreased sex drive, difficulty maintaining erections and a decrease in the amount of semen. These adverse sexual side effects are typically seen in less than 5% of men on the drug.

There is also a link to mental health effects, including depression. However, it’s unclear how common those are and if the drug itself is to blame.

“Certainly the vast majority of my patients have no such side effects and are fine and do pretty well with it,” said Colavincenzo.

If men are already dealing with sexual issues, Colavincenzo cautions against using the medication.

“I’m very cautious if a person tells me they’re having issues with sexual function,” she said. “I usually say I don’t think this is a good idea and I wouldn’t recommend it for them.”

Shapiro says the risk of permanent side effects is “so, so rare.”

“I’ve never seen it in a patient, and I’ve treated thousands of patients,” Shapiro said.

This article was originally published on NBCNews.com