If your hairline is receding and you’re are thinking about taking Merck’s baldness drug Propecia, you might want to think again. The U.S. Food and Drug Administration (FDA) ordered drug maker Merck to change the warning labels for Propecia and its prostate drug Proscar to include “libido disorders, ejaculation disorders and orgasm disorders,” conditions that FDA notes may continue well after patients stop taking the drugs. While FDA says it isn’t clear whether finasteride, the active chemical in Propecia and Proscar, is what causes the persistent sexual problems, side effects reported by those using the drugs “suggest a broader range of adverse effects than previously reported in patients taking these drugs.” FDA approved Proscar in 1992 and Propecia in 1997. Since then, the agency has reviewed 421 post-marketing reports of sexual dysfunction from those taking Propecia between 1998 and 2011. Of those, 59 cases described sexual dysfunction lasting a minimum of three months after discontinuing Propecia. FDA reviewed 131 reports of similar problems associated with Proscar. In 2011, FDA ordered the warning labels of both product be revised to include erectile dysfunction that continues after patients stop taking the drug. People can report adverse side effects of prescription drugs to FDA’s MedWatch hotline at 1-800-332-1088, report them online at MedWatch Online or through the U.S. mail using the MedWatch form (pdf) available at FDA’s website.