M

en who take a popular class of drugs to combat hair loss or prostate shrinkage may be at a small increased risk for long-lasting erectile dysfunction if they take the drug for a long time, a new study found.

Why it matters:

The FDA label for Propecia, one of the drugs in question, does note that adverse reactions include “sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders.” Still, Dr. Steven Belknap, a research assistant professor at the Northwestern University Feinberg School of Medicine, said men don’t know enough about possible side effects. He’s the senior author on the paper published Thursday in PeerJ.

The nitty-gritty:

Motivated by a buddy who asked for his professional advice about whether he should take the drug finasteride for baldness, Belknap scoured patient records at Northwestern. He looked for all men who were taking either finasteride or dutasteride, which work in similar ways in the body, and who did not have erectile dysfunction. He found 11,909 of them.

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Then he ran all sorts of statistical tests, and found that, among men who did not have prostate disease, those taking either drug for more than 208.5 days, or about seven months, had a statistically significant higher chance of developing “persistent erectile dysfunction” (which means the problem lasts for more than 90 days after you stop taking the drug).

It’s important to note that the rate of persistent erectile dysfunction in both groups was still quite low. Just 1.3 percent of men who took one of the drugs for more than 208.5 days had that problem. As did just 0.44 percent of the group that took one of the drugs for less time.

But keep in mind:

The study relied on patient records, so it has weaknesses.

Some men may have stopped taking finasteride immediately after experiencing negative reactions, which could have the effect of minimizing Belknap’s count of unpleasant side effects. On the other hand, his count could be inflated if he erroneously included in his study men who had erectile dysfunction even before they started taking the drugs, but didn’t have that information recorded in their medical records.

The study was funded in part by the Post-Finasteride Syndrome Foundation, a nonprofit that funds research to help men who have taken finasteride and experienced “persistent sexual, neurological, and physical adverse reactions,” according to the organization’s website. Additional funding came from the National Institutes of Health.

What they’re saying:

Researchers unaffiliated with the study could not be reached for comment Wednesday evening.

But others have published related research with similar findings. A 2015 paper, for instance, found that men with enlarged prostates who took finasteride experienced a decrease in erectile function as well as a decrease in testosterone levels over four years.

The presidential prescription:

Side note: One of the most famous patients on this type of drug may be President Trump. In February, the New York Times reported that the president takes a “small dose” of finasteride, citing Dr. Harold Bornstein, who served for decades as his personal doctor.

The bottom line:

Drugs designed to treat baldness and an enlarged prostate may have long-lasting effects on men’s reproductive health, but more research will be needed.

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