TL;DR: Since Merck clinical trials in the 1990s, there have been observations and reports of lasting sexual dysfunction in men who stopped taking finasteride. Finasteride and dutasteride have been associated with penile abnormalities. Taking finasteride can affect semen quality and fertility. There is no known effective treatment for lasting dysfunctions after stopping finasteride.
The points below are based on firsthand reports, adverse event reports to FDA, published research, doctors’ perspectives, the FDA-approved drug label and personal experience. These points concern finasteride as a treatment for hair loss in younger men.
- Finasteride lowers availability of the androgen dihydrotestosterone, or DHT, by inhibiting an enzyme. Read more about how finasteride works here.
- Some men who took finasteride and then discontinued the drug have reported severe adverse effects which do not respond to treatment, do not resolve over time, and may be irreversible. See firsthand experiences and adverse event data.
- Regarding sexual dysfunction that persists after stopping finasteride:
- The drug label approved by the U.S. Food & Drug Administration includes reports of sexual adverse effects that “continued after stopping the medication.”
- A recent systematic review included 11 studies which described men experiencing irreversible sexual adverse effects after stopping finasteride.
- In Merck Phase III clinical trials, there were 16 men who had drug-related sexual adverse events while on finasteride, which were not resolved at the end of treatment. In addition, there was one man who discontinued the trial due to a drug-related sexual adverse experience, and it was not resolved six months after discontinuing treatment (2007 Merck letter to Swedish regulatory authority).
- A separate Merck-sponsored clinical trial reported that one man’s drug-related sexual adverse experience on finasteride did not resolve with continued treatment (Overstreet et al., 1999).
- Beyond loss of sexual function and sexual desire, men have reported neuropsychiatric, cognitive, sensory and physical symptoms as well as sleep problems that continue after stopping finasteride (see lasting dysfunctions).
- There is no way to assess your risk of lasting dysfunctions after stopping finasteride or dutasteride (another drug with a similar pharmacology).
- There is no effective treatment for these lasting dysfunctions.
- Men have reported lasting dysfunctions after taking as little as one pill of finasteride.
- There is no published evidence that that taking finasteride at a lower dose or lower frequency would reduce the risk of lasting dysfunctions.
- A paper found that among younger men, longer duration on finasteride was the strongest predictor of developing erectile dysfunction that continues after stopping the drug (Kiguradze et al., 2017).
- Animal and human research has found finasteride and dutasteride treatment are associated with changes to the penis including reduced size, curvature and tissue changes including fibrosis and loss of smooth muscle. Read the research
- Regarding semen, sperm and fertility:
- There have been reports to FDA of malformed embryos and spontaneous abortion following paternal exposure to finasteride (Zakhem et al., 2019). The review, published in the Journal of the American Academy of Dermatology, noted: “spontaneous abortion…may be a risk associated [with] finasteride use.”
- At a higher dose of 5 mg, after 26 weeks men who took finasteride had reduced sperm count, concentration, motility (movement) and semen volume. 52 weeks into treatment, three of these four parameters returned to normal range; sperm motility did not improve. 24 weeks after stopping treatment, sperm motility remained significantly lower than before starting finasteride treatment. (Amory et al., 2007).
- The only clinical trial of effects of finasteride on semen parameters (Overstreet et al., 1999) lasted less than a year (48 weeks). There are no published trials on long-term effects of finasteride use on semen parameters or fertility.
- A 2013 study concluded: “Finasteride should be…used with caution in men who desire fertility.” (Samplaski et al., 2013)
- A male fertility center at Cornell recommends (emphasis added): “Do not use finasteride (Propecia, Proscar) for hair loss. There is accumulating evidence that it negatively impacts male fertility.”
- In June 2021, FDA added a new adverse event to the Postmarketing Experience section of the Propecia (finasteride 1 mg) label: hematospermia, or blood in semen.
- Based on anecdotal evidence: If you decide to take finasteride, stopping and restarting the drug could increase your risk of lasting dysfunctions.
- In 2021, an international group of doctors and researchers published diagnostic criteria for post-finasteride syndrome (Healy et al., 2021).
- Propecia label (excerpt)
- How was finasteride invented?
- Research review: Alterations to penile and prostatic tissue associated with finasteride and dutasteride treatment
- Adverse event data
- About lasting dysfunctions after use of finasteride or dutasteride
- Firsthand experiences on and off finasteride
- Research by system and function
Khera M, Than JK, Anaissie J, et al. Penile vascular abnormalities in young men with persistent side effects after finasteride use for the treatment of androgenic alopecia. Transl Androl Urol. 2020. DOI • PubMed
Saengmearnuparp T, Lojanapiwat B, Chattipakorn N, Chattipakorn S. The connection of 5-alpha reductase inhibitors to the development of depression. Biomed Pharmacother. 2021 Aug 31. DOI • PubMed • Full text via ScienceDirect
Schifano N, Capogrosso P, Boeri L, et al. Are finasteride-related penile curvature/Peyronie’s disease adverse event reports worthy of further clinical investigation? Disproportionality analysis based on both the Food and Drug Administration (FDA) and the European Medicines Agency (EMA) pharmacovigilance databases. Int J Impot Res. 2022. DOI • PubMed