For the study, researchers at Northwestern University looked at a cohort of 15,634 men exposed to finasteride who had no prior sexual dysfunction. Of these, 699 (4.5%) developed new ED and 210 (24.3%) developed new low libido.
Out of 11,909 men who used finasteride and had no prior sexual problems, 167 (1.4%) developed persistent erectile dysfunction that lasted for 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 a nearly 5-fold increased risk of persistent ED compared to men who used the medications 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 U.S. Food & Drug Administration (FDA) in 1997. It is a lower dose of Proscar (finasteride 5-mg), a drug used to treat enlarged prostate.
FDA has published multiple warnings about the link between Propecia and sexual dysfunction. In 2011, the agency revised 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 adverse event reports concerning serious sexual side effects.
The new study also found that the length of time that men took finasteride was a more accurate predictor of persistent sexual dysfunction than other known risk factor such as age, hypertension, type 2 diabetes, cigarette smoking, alcohol abuse, obesity and depression.
“We expect that our finding of an association between debilitating sexual dysfunction and exposure to finasteride or dutasteride will be of particular interest to prescribers and patients,” the researchers concluded.