Can finasteride cause erectile dysfunction?

Finasteride and Erectile Dysfunction

Yes, finasteride can cause erectile dysfunction, with approximately 4-15% of patients experiencing this side effect during treatment. 1, 2

Incidence and Risk

• Erectile dysfunction occurs in approximately 4.7% of patients during the first 6 months of treatment, with the incidence decreasing over time 3
• Clinical trials consistently show a 2-4% higher incidence of erectile dysfunction in patients taking finasteride compared to placebo 1
• The risk appears higher in patients taking finasteride for benign prostatic hyperplasia (BPH) compared to those taking it for male androgenetic alopecia (hair loss) 4
• In the Prostate Cancer Prevention Trial (PCPT), 67.4% of men on finasteride reported erectile dysfunction compared to 61.5% on placebo (relative risk 1.10) 1

Mechanism and Duration

• Finasteride inhibits 5-alpha-reductase enzyme, which converts testosterone to dihydrotestosterone (DHT), potentially affecting sexual function 1

• Sexual side effects typically include:

  • Erectile dysfunction 1, 2
  • Decreased libido (reported in 3% of patients initially) 3
  • Ejaculation disorders including reduced ejaculate volume (reported in 1.4-4.4% of patients) 1, 3

• While most guidelines suggest these effects are reversible and decrease over time 1, some research studies report cases of persistent sexual dysfunction:

  • Some patients report sexual side effects persisting for months or years after discontinuation 5, 6
  • In one study, 96% of subjects with persistent sexual side effects continued to experience them at reassessment 14 months later 6

Clinical Considerations

• The FDA label acknowledges that sexual dysfunction may continue after discontinuation of treatment, including erectile dysfunction and decreased libido 2
• The magnitude of sexual dysfunction effect is relatively small compared to natural sources of variability; on a scale of 0-100, finasteride's effect on sexual functioning was a mean difference of 3.21 points, compared to 1.26 points for each year of aging 1
• Discontinuation rates due to adverse events are approximately 6-7% in both finasteride and placebo groups 1

Nocebo Effect Consideration

• A significant nocebo effect may contribute to the reported sexual side effects
• One study found that patients informed about potential sexual side effects reported significantly higher rates (43.6%) compared to uninformed patients (15.3%) 7
• This suggests that patient expectations may influence the perception and reporting of sexual side effects

Recommendations for Clinical Practice

• Physicians should discuss the potential risk of sexual side effects with patients before starting finasteride therapy 2, 8
• For BPH treatment, consider that finasteride is less effective than alpha blockers for symptom improvement but reduces risk of disease progression 1
• For patients concerned about sexual side effects, consider alternative therapies, especially when treating androgenetic alopecia 8
• Monitor patients for development of sexual dysfunction during treatment 2
• Be aware that some patients may experience persistent sexual side effects even after discontinuation of the medication 2, 5, 6