Sexual side effects from finasteride can last longer than expected

How many men would willingly trade in their sex drive for a full head of hair? For some, that might seem like a deal with the devil.

Evidence is accumulating, though, that at least a few men make such a Faustian exchange when they accept a prescription for finasteride. This medication is used to reverse male pattern baldness (as Propecia) or control the symptoms of prostate enlargement (as Proscar). A related drug, dutasteride (Avodart), is also used to treat an enlarged prostate.

These drugs work by blocking the conversion of the male hormone testosterone to its byproduct dihydrotestosterone (DHT). Research has shown that DHT contributes to both male pattern baldness and prostate gland growth. Blocking DHT production can help men hang on to their hair longer as well as keep their prostates from expanding.

The problem is that there are side effects. The most notable are decreased libido, trouble with ejaculation and erectile dysfunction. These are thought to be uncommon, however, and physicians have assumed that they would disappear once the drug was discontinued.

The official prescribing information for Propecia is confusing on this matter. On the one hand, doctors are told that sexual side effects resolve when the drug is stopped. On the other hand, there is a suggestion that sexual dysfunction may persist "after discontinuation of treatment." This mixed message puts doctors and patients in a double bind.

A study published in the Journal of Sexual Medicine (online, July 12, 2012) suggests that some men may suffer long-lasting complications after quitting finasteride. Dr. Michael Irwig recruited young, healthy subjects who had taken Propecia for hair loss. Their average age was 31, and they had not experienced sexual problems before taking this medication. All of the volunteers in this study had complained of erectile dysfunction or other sexual difficulties while taking the drug and for a time after stopping.

The surprising finding from this research is that 96 percent of these otherwise healthy young men were still having significant sexual problems roughly a year after Irwig enrolled them in the study. He is concerned that in some cases such sexual side effects could be permanent.

Men reported lowered sex drive, reduced arousal, erectile dysfunction, impaired sensation and less satisfaction with orgasm. They also complained of semen quality, penis curvature and decreased testicular size. Some men had more difficulty sleeping or became depressed after taking finasteride.

Research in rats given the similar drug dutasteride shows a biological basis for erectile problems (Journal of Sexual Medicine, July 2012). Like the men in Irwig's study, the rats continued to have erectile difficulties long after the medication was withdrawn.

The proportion of men experiencing such long-lasting sexual complications is not yet known. It may be extremely small. Nonetheless, physicians and patients should be aware of the potential for persistent sexual harm before embarking on a medication that is being used purely for cosmetic purposes.

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Sexual side effects from finasteride can last longer than expected