Sexual side effects are the question men ask most about finasteride, and it deserves a direct answer. The honest one has three parts: placebo-controlled trials show a small excess of sexual side effects; part of that excess appears to be expectation; and the evidence that symptoms last after stopping is weaker than the online claims suggest.
What placebo-controlled trials show
A systematic review and meta-analysis of 15 randomized, placebo-controlled trials with 4,495 men in androgenetic alopecia found a relative risk of 1.66 (95% CI 1.20 to 2.30) for sexual adverse events with finasteride, based on 11 trials. For dutasteride 0.5 mg, based on 5 trials, the relative risk was 1.37 (95% CI 0.81 to 2.32), which is not statistically significant. Relative risks say how much more often events occur, not how often they occur in absolute terms.
The nocebo question
A randomized study of finasteride 5 mg (a dose used for prostate enlargement, not hair loss) asked whether men who were told about sexual side effects reported more of them. In its blinded administration, men informed about the side effects reported significantly more sexual dysfunction than men who were not told. The authors concluded that part of the effect is not a direct pharmacological action of the drug.
This does not mean the side effects are imaginary. It means that expectation adds to them, and that a clear, balanced conversation before treatment is part of safe prescribing.
Persistence after stopping
Irwig followed 54 men who had stopped finasteride because of sexual side effects that lasted at least three months. At follow-up, about 14 months after stopping on average, 96% still had persistent sexual side effects, and 89% met a definition of sexual dysfunction. The study had no control group and enrolled men who had already reported problems, so it cannot show that finasteride caused those symptoms, and the sample is not representative of all users.
Placebo-controlled data on persistence are limited and mixed. Some reviews argue that earlier studies that reported persistence have important biases and small samples. This is an open question, and we do not present it as settled in either direction.
Who should not take it
Finasteride is not for everyone. Our physicians review your history before any prescription, including liver problems, previous reactions to the medicine, prostate findings, and any use of other 5-alpha reductase medicines. Labeling advises that women who are pregnant or may become pregnant should not take finasteride tablets.
Labeling also advises that women who are or may become pregnant should not handle crushed or broken finasteride tablets, because the medicine can be absorbed through the skin and may harm a male fetus. Intact coated tablets are handled differently. If a pregnant woman has contact with a crushed or broken tablet, the area should be washed with soap and water and she should contact a doctor.
What this does not say
- The trial rates come from 1 mg and 5 mg studies and from populations that met each trial’s criteria. They are not a rate for a compounded product or for every person.
- A relative risk is not an absolute risk. The absolute rates in the pivotal trials are small, but the source we checked does not report them directly, so we do not quote them here.
- Persistence data come from a small uncontrolled study and from reviews that disagree about it.
- Topical finasteride has a lower systemic exposure in its phase III trial; it does not mean side effects are absent.
How our physicians use this
We discuss sexual side effects before the first prescription, in plain terms and with the numbers above, including the nocebo effect. We agree on what you would do if a side effect appears, and we check in on schedule rather than waiting for you to raise it.
If you have concerns about your history, your partner’s pregnancy plans, or any symptom after starting, tell us. Your physician decides whether finasteride, a different form or a different approach fits you.
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- 1.Lee S et al. Adverse sexual effects of treatment with finasteride or dutasteride for male androgenetic alopecia: a systematic review and meta-analysis. Acta Derm Venereol 2018;99(1). Acta Dermato-Venereologica
- 2.Finasteride 5 mg and sexual side effects: how many of these are related to a nocebo phenomenon? J Sex Med 2007. PubMed
- 3.Irwig MS. Persistent sexual side effects of finasteride: could they be permanent? J Sex Med 2012;9(11). George Washington University
- 4.PROPECIA (finasteride) tablet, film coated. Prescribing information, Organon LLC. DailyMed, NLM