Some active men take anti-balding drugs such as Proscar, Propecia and Avodart. These drugs are classified as 5-alpha-reductase inhibitors that reduce the conversion of testosterone to dihydrotestosterone. They are also used to treat prostate enlargement and cancer.
Many men report that anti-balding drugs decrease sex drive and erection capacity. A study on rats from the Tulane Health Science Center in New Orleans showed that animals treated with dutasteride (a 5-alpha-reductase inhibitor) showed decreased erectile capacity, and the drug interfered with chemicals controlling blood flow to the penis. The U.S. Food and Drug Administration issued a warning that anti-balding drugs can cause erection problems that can persist even after going off the medications. (Journal Sexual Medicine, 9: 1773-1781, 2012; “Good Morning America,” July 12, 2012)