Persistent erectile dysfunction in men exposed to the 5α-reductase inhibitors, finasteride, or dutasteride
Tina Kiguradze, William H. Temps, Paul R. Yarnold, John Cashy, Robert E. Brannigan, Beatrice Nardone, Giuseppe Micali, Dennis Paul West, Steven M. Belknap
PeerJ2017
In plain terms
Researchers went through the medical records of about 12,000 men at one Chicago health system who had been prescribed finasteride or dutasteride. About 1 in 70 developed erection problems that were still being recorded at least three months after they stopped the drug, and for half of them the problems were still noted more than three and a half years later. The longer men had taken the drug, the more likely this was: among men under 43 on the hair-loss dose, about 1 in 86 who took it for more than about seven months had lasting erection problems, compared with about 1 in 424 who took it for less.
What it doesn’t show: It can't prove the drug caused the problems: it used existing records, not a trial, and it only counted erection problems that a doctor wrote down and treated with an erection drug, so it says nothing about other reported symptoms such as low mood or genital numbness.
Summary (paraphrased)
Using electronic medical records from Northwestern Medicine, the authors tested whether longer 5-alpha-reductase inhibitor exposure raises the risk of persistent erectile dysfunction (PED, lasting at least 90 days after stopping the drug). Among 11,909 exposed men, 167 (1.4%) developed PED with a median persistence of about 1,348 days after discontinuation; roughly a third of men with new erectile dysfunction had the persistent form. Classification-tree modelling identified exposure duration, prostate disease, age, and NSAID use as predictors. In men aged 16–42 on the hair-loss dose, PED occurred in 1.16% of those with more than 205 days of exposure vs 0.24% with less (about 4.9-fold); the paper also reports a 4.8-fold risk for men without prostate disease taking NSAIDs with more than ~208 days of exposure, a figure that by its own counts compares them with men not taking NSAIDs (against shorter exposure in the same group it is about 2.5-fold). The authors conclude that the findings contradict label claims that longer exposure does not increase risk and that sexual effects resolve on discontinuation.
Evidence
Extracted from the full text; page numbers refer to the paper. The library’s own notes are labelled as such.
- Design
- Cohort studyRetrospective cohort study of electronic medical records, comparing longer with shorter exposure within exposed men (classification tree analysis)
- Setting
- Northwestern Medicine Enterprise Data Warehouse (Chicago, USA), records 1992–2015
- Population
- Men aged 16–89 prescribed finasteride or dutasteride, with no recorded erectile dysfunction, low libido or PDE5 inhibitor use before their first prescription. Subgroup: men aged 16–42 taking only finasteride at 1.25 mg/day or less (the hair-loss dose; 5 mg tablets were often split).
- Size
- 11,909 · 11,909 men evaluated for persistent ED, from 17,475 exposed among 691,268 men in the records; subgroup 4,284
- Exposure
- Finasteride (≤1.25 mg/day or higher doses) or dutasteride; duration counted from first prescription
- Compared with
- Men in the same cohort with shorter exposure (no unexposed group in the main analysis)
- Outcome
- Persistent erectile dysfunction: a new ED diagnosis with a PDE5 inhibitor prescription, and a physician's note of ED lasting at least 90 days after stopping the drug (the FDA's criterion), confirmed by two reviewers. Secondary: new ED, new low libido.
- Follow-up
- Persistent ED assessed in records from January 1992 to September 2013
Key results
- Persistent ED in 167 of 11,909 men (1.4%); median persistence 1,348 days after stopping (IQR 631.5–2,320.5) · p. 12
- 167 of the 530 men with new ED (31.5%) had the persistent form · p. 12
- Men without prostate disease who also took NSAIDs: persistent ED in 2.1% (26 of 1,231) with more than 208.5 days of exposure vs 0.83% (19 of 2,294) with shorter exposure. The paper reports a 4.8-fold risk (NNH 59.8; p < 0.002); those figures match a comparison with men without prostate disease who took no NSAIDs (0.44%, 19 of 4,331), not with the shorter-exposure NSAID group (about 2.5-fold) · pp. 17–18, Fig. 2A
- Men aged 16–42 on finasteride ≤1.25 mg/day: persistent ED in 34 of 4,284 (0.79%), median 1,534 days; more than 205 days of exposure 1.16% (30 of 2,587) vs 0.24% (4 of 1,697) with shorter exposure, 4.9-fold (NNH 108.2; p < 0.004) · p. 18, Fig. 2B
- Exposure duration predicted persistent ED better than age, hypertension, diabetes, smoking, alcohol misuse, obesity and depression; only prostate disease and prostate surgery predicted it better · pp. 17, 19
Limitations the authors note
- Possible confounding by factors linked to 5-ARI use; NSAID use may reflect why NSAIDs were prescribed rather than an effect of them
- Detection depended on what clinicians recorded; no validated questionnaire such as the IIEF was available
- With no unexposed group in the main analysis, the NNH is an upper bound; the authors expect a placebo-controlled trial would show a higher risk
- The exposure cutpoints (about 205–208 days) are not safe thresholds
- Other reported effects (cognitive, psychological, genital numbness, other sexual effects) were not studied
- Older men probably under-report sexual problems
Also worth weighing (library’s note)
- One US health system; results may not generalise
- Persistent ED required a PDE5 inhibitor prescription, so untreated cases were not counted
- Exposure is measured from prescriptions, not from whether the drug was taken
- The analysis method (optimal discriminant / classification tree analysis) is uncommon, and its cutpoints are derived from the data
Funding: US National Institutes of Health grants, and a gift from the Post-Finasteride Syndrome Foundation; the authors state the funders had no role in the study. Interests: One author (Yarnold) is an employee of Optimal Data Analysis, LLC
What it can support (library’s note): An association between longer finasteride or dutasteride use and erectile dysfunction that persists after stopping, in routine care. It does not establish causation, and its rates are not population-wide frequencies.
Why it’s in the corpus
The largest exposure-outcome study of persistent ED after 5-ARI use, providing duration-response evidence and number-needed-to-harm estimates — the core pharmacoepidemiologic anchor for PFS persistence claims.
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