The prescribing information for Propecia (finasteride 1 mg) reports drug-related adverse experiences in Year 1 for Propecia (N=945) versus placebo (N=934), including decreased libido (1.8% versus 1.3%), erectile dysfunction (1.3% versus 0.7%) and ejaculation disorder (1.2% versus 0.7%). A 2026 systematic review of placebo-controlled trials of oral finasteride 1 mg in men with androgenetic alopecia reported sexual adverse events in 1.9-6.7% of treated patients compared with 0.9-3.9% in placebo groups. The label also lists sexual dysfunction that continued after discontinuation of treatment, based on reports after approval.
What the label reports from its 12-month trials
| Drug-related adverse experience, Year 1 | Propecia (N=945) versus placebo (N=934) |
|---|---|
| Decreased libido | 1.8% versus 1.3% |
| Erectile dysfunction | 1.3% versus 0.7% |
| Ejaculation disorder (decreased volume of ejaculate) | 1.2% (0.8%) versus 0.7% (0.4%) |
| Discontinuation due to drug-related sexual adverse experiences | 1.2% versus 0.9% |
In an integrated analysis, 36 (3.8%) of 945 men treated with Propecia reported one or more of these adverse experiences, compared with 20 (2.1%) of 934 men treated with placebo (p=0.04). Across three controlled clinical trials of 12-month duration, 1.4% of patients taking Propecia (n=945) were discontinued due to drug-related adverse experiences, compared with 1.6% for placebo (n=934). The label also says resolution occurred in men who discontinued therapy due to these side effects and in most of those who continued therapy, and that the incidence of each decreased to ≤0.3% by the fifth year of treatment.
On a self-administered sexual function questionnaire at Month 12, the label reports statistically significant differences in favor of placebo in 3 of 4 domains (sexual interest, erections, and perception of sexual problems), with no significant difference in overall satisfaction with sex life.
What the label lists from reports after approval
Under use after approval, the label lists sexual dysfunction that continued after discontinuation of treatment, including erectile dysfunction, libido disorders, ejaculation disorders, and orgasm disorders. Its Patient Information lists, among effects reported in general use, problems with ejaculation and difficulty in achieving an erection that continued after stopping the medication, and male infertility and/or poor quality of semen.
The label states these reactions are reported voluntarily from a population of uncertain size, so it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.
What reviews of randomized trials found
The same 2026 review described most events as mild and reversible upon discontinuation. It concluded that clinicians should counsel patients that most sexual side effects reported in controlled studies are infrequent, mild, and reversible, but individual susceptibility varies.
A 2019 meta-analysis of fifteen randomized double-blinded placebo-controlled trials (4,495 subjects) of 5-alpha-reductase inhibitors found a 1.57-fold risk of sexual dysfunction (95% confidence interval 1.19-2.08). The relative risk was 1.66 (95% CI 1.20-2.30) for finasteride and 1.37 (95% CI 0.81-2.32) for dutasteride.
A 2016 meta-analysis of randomized trials reported pooled relative risks for sexual dysfunction of 2.56 (95% CI = 1.48-4.42) in men with enlarged prostate (BPH) and 1.21 (95% CI = 0.85-1.72) in men with androgenetic alopecia. Its authors concluded the association was not statistically significant in men with androgenetic alopecia.
What safety reporting and databases add
A 2015 meta-analysis of 34 finasteride trials found that none had adequate safety reporting, 19 were partially adequate, 12 were inadequate, and 3 reported no adverse events. It found funnel plots with a bias toward lower odds ratio for sexual adverse effects, suggesting systematic underdetection.
A retrospective cohort study in a U.S. health claims database compared 1390 men who had stopped using finasteride 1 mg with 20,000 randomly selected age- and calendar time-matched users of omeprazole from 2006 to 2014. The rate of persistent sexual dysfunction was 37.9 per 1000 person-years for finasteride 1 mg users and 15.0 for omeprazole users, with an adjusted hazard ratio of 1.62 (1.14-2.29). The study used a claims-based definition: a sexual dysfunction diagnosis code plus use of a phosphodiesterase inhibitor (sildenafil, tadalafil, or vardenafil). This is an observational study and cannot show cause and effect.
A pharmacovigilance analysis of FDA Adverse Event Reporting System reports found more than expected reporting of sexual dysfunction with low-dose finasteride in young men compared with all other drugs in the database (EBGM 28.0, 95% CI 26.1-30.0). Such reports cannot establish how often the problem occurs.
What this does not tell you
These figures come from different designs, lengths and comparison groups, so they should not be added together or ranked. The label compares with placebo, the claims study with omeprazole users, and the reporting analysis with all other drugs. Observational and spontaneous-report data cannot show cause and effect. None of these sources tells a man his own chance of a sexual side effect, and the two meta-analyses above reported different results for men with hair loss. This guide covers sexual effects only. The hair outcomes the trials measured are covered in a separate guide, and both belong in a conversation with a licensed provider.