The widely used baldness drug finasteride (Propecia) indeed boosts hair growth in men, but some may develop sexual problems, according to a new analysis.

A review of recent research found that men with the most common form of baldness who took finasteride are more likely to experience an increase in hair count, and say they believe their hair is thicker. But approximately 1 in 80 also experience erectile dysfunction, according to the analysis published in the Archives of Dermatology.

However, men with sexual side effects were not more likely to stop taking the drug. “It seems that most men taking this drug really prefer to have hair,” study author Dr. José Manuel Mella of the Hospital Alemán in Buenos Aires told Reuters Health.

Up to half of men will experience pattern hair loss - known clinically as androgenetic alopecia - by the age of 50. Finasteride works by blocking an enzyme that converts testosterone into dihydrotestosterone, the hormone responsible for hair loss.

Several studies have investigated the effectiveness of finasteride, which costs about $50 per month for a brand-name pill but less for a generic version. However, questions have remained over its potential side effects.

To help answer these questions, Mella and his team scanned the medical literature and analyzed the findings of 12 studies that included 3927 men.

They found that men taking finasteride notice a 30% improvement after two years. “Finasteride has a tendency to maintain and improve hair count over time while being on treatment,” Mella said in an email. “The longer you treat, the bigger the effect.”

However, finasteride did appear to increase the risk of sexual side effects, affecting 1 in 80 men taking the drug. “Patients must discuss their preferences with their doctors,” the researcher advised.

Mella and his team rated most of the data included in the current study as “moderate quality,” meaning the results may have been affected by factors such as bias (if funded by the sellers of finasteride, perhaps). However, any impact would be relatively minor, and the data are reliable overall, noted Mella, who did not receive any funding from the makers of finasteride to produce his paper. “Our results are probably accurate.”

Dr. Matt Leavitt, who co-authored one of the studies included in the new analysis, said he wasn’t surprised by the findings, and prescribes finasteride “pretty much daily” to his patients.

Indeed, “there is an occasional patient that does describe a sexual side effect,” noted Leavitt, medical director of the Advanced Dermatology & Cosmetic Surgery Clinic based in Florida and president of the Hair Foundation. But most are willing to try the drug knowing they can just stop taking it if any problems arise. “We know that it works on most patients.”

SOURCE:  Archives of Dermatology, October 2010.