For the study, researchers at Northwestern University examined a cohort of 15,634 men exposed to finasteride who had no previous sexual dysfunction. Of these, 699 (4.5%) developed new ED and 210 (24.3%) developed a new low libido.
Of the 11,909 men who used finasteride and had no previous sexual problems, 167 (1.4%) developed persistent erectile dysfunction lasting at least 90 days after discontinuing treatment.
The researchers also determined that younger men who took finasteride or dutasteride for more than 205 days had an almost 5-fold increased risk of persistent ED compared to men who used the drugs for shorter intervals.
Propecia (finasteride 1-mg) is a treatment for male pattern baldness that was created by Merck & Co. It works by inhibiting dihydrotestosterone (DHT), a hormone that causes hair loss in men with a genetic predisposition. Propecia was approved by the Food and Drug Administration (FDA) in 1997. It is a lower dose of Proscar (finasteride 5 mg), a drug used to treat enlarged prostate.
The FDA has issued multiple warnings about the link between Propecia and sexual dysfunction. In 2011, the agency reviewed the labeling of Propecia to include erectile dysfunction that persisted after the drug was discontinued. In April 2012, the FDA added new warnings after receiving 421 reports of adverse events on serious sexual side effects.
The new study also found that the time men took finasteride was a more accurate predictor of persistent sexual dysfunction than another risk factor known as age, hypertension, type 2 diabetes, smoking, alcohol abuse, Obesity and depression.
“We hope that our finding of an association between the weakness of sexual dysfunction and exposure to finasteride or dutasteride will be of particular interest to prescribers and patients,” the researchers concluded.