Male hair loss is often treated with a drug called finasteride. It blocks 5alpha-reductase in the scalp and male reproductive organs, inhibiting the conversion of the male hormone testosterone to its more potent form, 5alpha-dihydrotestosterone (5alpha- DHT). Men who take finasteride experience a 70% reduction in the amount of 5alpha-DHT in their blood. The Northwestern University study has revealed that not one of the 34 published clinical trial reports of finasteride's sexual dysfunction side effects provided adequate information about the severity, frequency or reversibility of sexual adverse effects.
The published clinical trial reports do not address key questions doctors and patients would want to know, such as how safe is finasteride? Is there a risk of developing sexual dysfunction in men who take finasteride? How severe is finasteride-associated sexual dysfunction in man? If a man gets sexual dysfunction while taking finasteride, will his sexual function return to normal when the drug is stopped? What is the risk of persistent sexual dysfunction associated with the use of finasteride?
Lead author Steven Belknap said, "People who take or prescribe the drug assume it's safe, but there is insufficient information to make that judgment. Of the 5,704 men in the Northwestern Medicine clinical data repository who were treated for male pattern baldness with finasteride, only 31% met inclusion criteria for the pivotal trials referenced in the manufacturer's Full Prescribing Information. Thus, the available information from clinical trials does not apply to most of these men in Northwestern's study population who took finasteride for male pattern baldness. For example, some men with hair loss who are taking finasteride have diabetes mellitus, high blood pressure or are taking other drugs such as diuretics or antidepressants that also increase the risk of sexual dysfunction. Duration of drug safety evaluation was limited to one year or less for 26 of 34 trials, but 33% of men in the Northwestern clinical data repository took finasteride for more than one year."
The study has been published in JAMA Dermatology.