Propecia and Proscar is made by pharmaceutical giant, Merck and is often prescribed for male pattern baldness and enlarged prostate or benign prostatic hyperplasia (BPH). The active ingredient in both drugs is finasteride. Propecia is the brand name of the 1-milligram tablet and Proscar is the 5-milligramt tablet.

Merck lists known serious side effects: cognitive impairment, depression and various forms of sexual dysfunction, including erectile dysfunction, reduced libido, and infertility. According to warnings, the sexual dysfunction side effects should “resolve after discontinued use of the drug.” But that may not be the case.

For last ten years, the Swedish Medical Products Agency has been following reports of men who continue to experience sexual dysfunction even after they stopped taking finasteride. Merck changed its label in several European countries, noting that sexual effects might be permanent; but label information in the United States has not been updated.

As an interesting side note Merck actively warns against pregnant women touching this drug. Research suggests that the active ingredient, finasteride, may cause abnormalities of a developing male baby’s sex organs.