Oral finasteride use and sexual adverse events: signal detection from disproportionality analyses of data from the United States Food and Drug Administration Adverse Event Reporting System

BACKGROUND: Oral finasteride 1 milligram (1 mg) daily-which is a 5-alpha reductase inhibitor (5-ARI) approved by the Food and Drug Administration (FDA) for androgenetic alopecia-is linked to sexual adverse events (AEs). However, it remains unclear whether this link is causal or merely correlational. METHODS: In FAERS, AEs are described by preferred terms (pts) of the Medical Dictionary for Regulatory Activities system; we investigated 8 AEs, including erectile dysfunction (pt = 10,061,461). We determined if signals could be detected with finasteride 1 mg-and 0.5 mg of dutasteride (a more potent 5-ARI)-in FAERS, for sexual AEs related to the post-finasteride syndrome (PFS): for the two, we identified the yearly number of cases (i.e. reports with sexual AEs) from 2006 to 2024. For each AE, we conducted a disproportionality analysis where reporting odds ratios (RORs) were estimated-along with p-values and 95% confidence intervals (CIs). RESULTS: There were more reports with finasteride 1 mg than with dutasteride 0.5 mg; for both, more reporting was observed as of 2012, the year the PFS foundation formally propagated PFS awareness. CONCLUSIONS: Our findings support that the disproportionately higher reporting of sexual AEs with finasteride 1 mg than with dutasteride 0.5 mg-even more so after 2012-could be attributed to the nocebo effect.