Propecia (finasteride) works by making massive changes to hormone levels in a man’s body, which can have unintended side effects on sexual function. It prevents the conversion of testosterone into more-potent 5α-dihydrotestosterone (5α- DHT), which reduces 5α- DHT levels by 70%.
None of the studies provided enough information about the severity, reversibility, or frequency of sexual side effects. Side effect reporting was “partially adequate” in 19 studies (56%), inadequate in 23 studies (35%), and 3 studies (9%) reported no adverse events.
Dr. Steven Belknap, lead author of the analysis, warned that there is insufficient information to assume Propecia is safe:
“Was this information obtained but then not included in published articles? Or, were these clinical trials performed in a way that simply didn’t capture this essential information? And most importantly, is the risk to benefit ratio of finasteride acceptable?”
In recent years, there has been growing concerns about long-term sexual dysfunction from Propecia. The FDA has already issued warnings about sexual side effects, including erectile dysfunction, low libido, ejaculation disorders, and orgasm disorders that continue after Propecia is discontinued.