Merck Warned Europe That Propecia Causes Sexual Problems -- but Not the U.S.

Last Updated Mar 22, 2011 9:50 AM EDT

Merck (MRK) has some explaining to do about why its warnings of the risk of persistent or permanent sexual dysfunction in men taking the hair loss drug Propecia are different depending on where you live and how much you take.

The official warning label for the drug in the U.S. says that sexual side effects -- such as erectile dysfunction -- occurred in less than 2 percent of men and that these side effects went away in men who stopped taking it. But a lawsuit filed in New Jersey federal court in February by two men who took Propecia claims that in the U.K., Sweden and Italy the Propecia warning label says that sexual dysfunction may be permanent. I first reported that Sweden required stricter warnings for the drug in January.

In addition, Merck's warning for the prostate drug Proscar -- which is the same chemical as Propecia, finasteride, except at a higher dose -- also warns of "prolonged adverse effects on sexual function such as erectile dysfunction and diminished libido."

The suit follows a recent study in the March issue of the Journal of Sexual Medicine which puts the rate of sexual dysfunction at 5-23 percent, with permanence in half of those. A 2008 study by the same authors put the rate at up to 38 percent. Merck said:

For men with male pattern hair loss, Propecia remains an important treatment option for appropriate patients. Merck encourages healthcare providers and consumers to report any adverse experience associated with any Merck medication or vaccine. Patients should talk with their healthcare providers if they have any questions about the benefits and risks of Propecia.
Separately, Kevin Nalty, Merck's former consumer product director on Propecia, who quit in May 2009 when his personal YouTube videos became too much a of a distraction for the company, revealed on his blog that he has had a hair transplant. Transplant surgeons recommend patients use Propecia to encourage hair to grow, he says.

As Nalty notes, there is a good reason why Propecia might damage sexual function: finasteride inhibits the enzyme that converts testosterone into dihydrotestosterone (DHT). DHT causes baldness. Unfortunately, DHT is also what men need to keep their mojo working.

For that reason, the suit claims, a small number of doctors including John Crisler of the "All Things Male -- Center for Men's Health" in Michigan, are refusing to prescribe Propecia:


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