Hair-growth drug linked to male sexual problems

According to a study released in the Journal of Sexual Medicine, the hair-growth drug finasteride, commonly marketed under the trademark name Propecia, can cause persistent sexual dysfunction well after you stop the medication.
Doctors have long known that finasteride can cause impotence and related sexual problems. Finasteride decreases the conversion of testosterone to the more potent dihydrotestosterone, the latter of which is related to hair loss. Yet any medication that interferes with testosterone runs the risk of also affecting sexual performance. 

In fact, GlaxoSmithKline and Merck, who both sell finasteride for several medical conditions, have reported that up to 8 percent of users have adverse sexual events.