Study: Sexual Side Effects of Hair Loss Drugs Persist

Analysis Suggests Lingering Side Effects of Drugs That Shrink Prostate and Treat Baldness

Medically Reviewed by Laura J. Martin, MD on March 09, 2011
From the WebMD Archives

March 9, 2011 -- Medications that shrink enlarged prostates and treat male pattern baldness can have sexual side effects that may persist after the drugs are discontinued, a new research review suggests.

But a manufacturer of one of the drugs says side effects go away when patients stop taking the drug. And an independent expert is skeptical of the study’s results.

The drugs, called 5-alpha-reductase inhibitors, block the action of the hormone dihydrotestosterone (DHT), an androgen that’s more potent than its precursor, testosterone.

This class of medications includes Avodart, Propecia, and Proscar.

According to the new review, which is published in the Journal of Sexual Medicine, long-term studies show that these medications can help shrink an enlarged prostate, a condition that affects as many as half of men over age 60, within three months to two years of use.

In other studies, about half of men who were taking Propecia for hair loss regrew some hair, while 42% saw no further hair loss, compared to those taking a placebo pill.

Additionally, a handful of studies have suggested that these kinds of drugs may lower the risk of prostate cancer, though that benefit is still controversial.

But the review says less attention has been paid to uncommon but potentially devastating side effects of these medications.

Those side effects can include anxiety, depression, loss of sex drive, difficulty getting or maintaining and erection, gynecomastia (growth of male breast tissue), and reduced semen production, which may affect fertility.

What’s worse is that for some, these side effects persist, even when they stop taking the medication, according to the review.

“We don’t really understand why, but the symptoms remain persistent or irreversible and even if they get off the drug,” says study researcher Abdulmaged M. Traish, PhD, a professor of biochemistry at the Boston University School of Medicine. “They no longer regain what they had before. Biologically, something gets shut off and gets shut off once and for all.”

Traish thinks that may be because nerves that are maintained by dihydrotestosterone become permanently degraded and can’t be repaired even after men come off the medication.

Expert Skeptical

Critics of the paper, however, called its conclusions biased and bizarre.

“If you subtract the placebo group, 3% to 4% of patients may have some sexual side effects, and they go away when you stop the drug,” says Patrick Walsh, MD, the University Distinguished Service Professor of Urology at Johns Hopkins in Baltimore, who also reviews studies for the journal Urology. “This is bizarre.”

“I’ve never seen a patient who had sexual side effects and when he stopped them he was impotent forever,” says Walsh.

When asked if he gets any financing from drug companies, he said, “Absolutely I do not. No.”

Walsh has researched the effects of 5-alpha-reductase inhibitors for 42 years and recently testified in FDA hearings against their proposed use for prevention of prostate cancer.

“If you take a look at the randomized, controlled trials, something like 3% of placebo and 6% of treated patients will have some sexual side effects,” Walsh tells WebMD. “It’s one of the reasons why patients discontinue the drug and when they discontinue it, the problem goes away.”

How Many Men Are Affected?

Merck, the company that makes Propecia, did not respond to calls and emails for comment in time for publication, but according to Propecia’s web site, sexual side effects -- including loss of desire, erectile dysfunction, and decreased semen production -- are uncommon, “each occurring in less than 2% of men.”

Additionally, “these side effects went away in men who stopped taking Propecia because of them,” the site says.

But studies included in the review found rates of erectile dysfunction related to the use of 5-alpha-reductase inhibitors that were significantly higher, in the range of 6% to 8%.

Traish thinks that may be because men who stop taking medications because of side effects may not have been counted in the final analysis.

Studies in the review also found that about 4% of men taking a 5-alpha-reductase inhibitor, compared to 2% of men taking a placebo, experienced reduced sex drive.

Another trial found that 4.5% of men taking Propecia experienced growth of breast tissue compared to 2.8% who were taking a placebo.

The review also reported that several smaller studies had noted significant increases in depression in men taking Propecia compared to those on a placebo.

Weighing Benefits and Risks

In what cases, then, would the benefits of being on these medications outweigh the potential risks?

“Someone who is a 69-year-old who has horrible benign prostatic hyperplasia, and he cannot urinate and he has to get up eight times a night to do that, I think the benefits outweigh the risks in this case,” Traish says. “But for a guy who is 39 years old with a little bit of receding hair line or a little bit of hair loss, I don’t think there’s any benefit that outweighs any risk at that point because the risk is far, far greater.”

And importantly, Traish thinks the dose of the drug may not matter. That is, lower doses may not be safer than higher doses in individuals who happen to be susceptible to side effects.

Traish says younger men who are thinking about taking the drug for cosmetic reasons ought to think twice.

“They ought to think three times, not just twice,” he says.

“Patients and doctors should not take this issue lightly. There should be honest, sincere, frank discussion before you put someone on these drugs.”

Show Sources


Traish, A. Journal of Sexual Medicine, 2011.

Abdulmaged M. Traish, PhD, professor of biochemistry, Boston University School of Medicine.

Patrick Walsh, MD, University Distinguished Service Professor of Urology, Johns Hopkins University, Baltimore.

Propecia web site.

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