Do sexual side effects of oral finasteride (Finasteride) improve or resolve with continued use over time?

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Last updated: September 28, 2026 • View editorial policy

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Sexual Side Effects of Oral Finasteride: Resolution Over Time

Sexual side effects from finasteride do decrease over time but do not completely resolve, and they remain statistically significant even with continued treatment. According to the highest-quality guideline evidence, while the incidence of new sexual adverse events is highest in the first year of therapy, these effects persist at a lower but measurable rate throughout long-term use 1, 2, 1, 2.

Evidence from Large-Scale Trials

The most robust data comes from the Prostate Cancer Prevention Trial (PCPT), which followed over 18,000 men for up to 7 years. The sexual dysfunction associated with finasteride decreased over time, although it remained statistically significant 1, 2. Specifically:

  • Year 1: 15% of finasteride-treated patients experienced drug-related sexual adverse events versus 7% on placebo (P <0.001) 3
  • Years 2-4: The incidence of new sexual adverse events dropped to 7% in both finasteride and placebo groups—meaning no additional difference between groups 3
  • However, pre-existing sexual dysfunction from year 1 often persisted

The magnitude of sexual dysfunction was relatively modest on a clinical scale. On a 0-100 scale (higher scores = more dysfunction), finasteride caused a mean difference of only 3.21 points compared to placebo—notably smaller than the 1.26-point difference associated with each additional year of age 1, 2.

Pattern of Sexual Side Effects

The sexual adverse events include 1:

  • Erectile dysfunction: 2-4% absolute increase over placebo
  • Decreased libido: 2-4% absolute increase over placebo
  • Decreased ejaculate volume: 2-4% absolute increase over placebo
  • Gynecomastia: ~2% absolute increase over placebo

Resolution Rates During Treatment

Among men who developed sexual side effects while on finasteride 3:

  • 12% experienced resolution while continuing therapy (compared to 19% on placebo)
  • Only 4% of finasteride patients discontinued due to sexual adverse events (versus 2% on placebo)
  • Of those who discontinued, 50% experienced resolution after stopping finasteride

Critical Caveats and Persistent Effects

Post-Finasteride Syndrome Controversy

The FDA has amended finasteride labels to include warnings about persistent sexual dysfunction after discontinuation 4, 5. Research studies have documented cases where sexual side effects persisted for months to years after stopping finasteride 6, 7, 8:

  • One study found 96% of men with persistent sexual dysfunction (≥3 months after stopping) continued to have symptoms at 14-month follow-up 7
  • Another reported persistent effects lasting a mean of 40 months after finasteride cessation 8

However, these studies have significant methodological limitations: post-hoc design, selection bias (men with persistent problems more likely to report), recall bias, and lack of baseline hormone measurements 6, 7, 8. The true incidence of persistent sexual dysfunction in the general population taking finasteride remains unclear.

Dose Considerations

The evidence primarily comes from 5 mg daily dosing (for BPH). For the 1 mg dose used for hair loss, one study showed similar PSA suppression effects in men ≥50 years 2, suggesting comparable biological activity, though long-term sexual side effect data at this dose are limited.

Clinical Approach

For patients starting finasteride:

  1. Counsel that sexual side effects are most common in year 1 (8% absolute increase over baseline rates)
  2. Explain that new sexual problems become much less likely after year 1, with incidence dropping to placebo levels
  3. Acknowledge that pre-existing sexual dysfunction may persist but often improves partially over time
  4. Discuss the controversial but documented cases of persistent dysfunction after discontinuation, though the true risk remains uncertain
  5. Consider baseline sexual function assessment to distinguish pre-existing from treatment-emergent dysfunction

For patients with sexual side effects on finasteride:

  • Approximately 1 in 8 will experience spontaneous resolution while continuing treatment
  • Discontinuation leads to resolution in about half of affected men
  • The other half may experience prolonged symptoms, though causality remains debated

The evidence does not support the common clinical assumption that "side effects always resolve with time." Rather, they decrease in frequency and severity but persist at detectable levels throughout treatment.

References

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