Can finasteride (Propecia) cause sexual dysfunction?

Finasteride and Sexual Dysfunction

Yes, finasteride can cause sexual dysfunction, with clinical trials demonstrating a 2-4% absolute increase in erectile dysfunction, decreased libido, and ejaculation disorders compared to placebo, though these effects typically diminish over time in most patients. 1

Incidence and Types of Sexual Dysfunction

The sexual side effects of finasteride are well-documented across multiple large-scale trials:

• Erectile dysfunction occurs in approximately 2-4% more patients taking finasteride compared to placebo 1, 2
• Decreased libido is reported in approximately 3% of patients initially 2
• Ejaculation disorders (including decreased ejaculate volume) occur in 1.4-4.4% of patients 2
• In the Prostate Cancer Prevention Trial (PCPT), 67.4% of men on finasteride reported erectile dysfunction versus 61.5% on placebo (relative risk 1.10), though this reflects baseline high rates of dysfunction in older men 2

Clinical Context and Magnitude of Effect

The absolute magnitude of sexual dysfunction attributable to finasteride is relatively modest when compared to natural aging:

• On a 0-100 scale measuring sexual dysfunction, finasteride produces a mean difference of 3.21 points compared to placebo 1, 2
• For comparison, each additional year of age contributes 1.26 points of sexual dysfunction 1
• This suggests the drug effect is approximately equivalent to 2-3 years of natural aging 1

Time Course and Resolution

Sexual dysfunction associated with finasteride typically decreases over time with continued treatment:

• Sexual adverse effects are most common during the first 6 months of treatment 2
• New reports of drug-related sexual adverse experiences decrease with duration of therapy 3
• The FDA label states "there is no evidence of increased sexual adverse experiences with increased duration of treatment" 3

Important Caveat: Persistent Sexual Dysfunction

The FDA label includes a critical warning about rare cases of persistent sexual dysfunction:

• Sexual dysfunction that continued after discontinuation of treatment has been reported in postmarketing surveillance, including erectile dysfunction, decreased libido, ejaculation disorders, and orgasm disorders 3
• These persistent effects have been reported "rarely" and their independent relationship to finasteride remains uncertain, particularly in older men with comorbidities and concomitant medications 3
• The FDA specifically notes this persistent dysfunction in the patient information for both BPH treatment and male pattern baldness 3

Discontinuation Rates

Overall discontinuation rates due to adverse events are modest:

• Approximately 6-7% of patients discontinue finasteride due to adverse events, which is similar to placebo discontinuation rates 1, 4
• This suggests that while sexual side effects occur, they are tolerable for most patients 1

Clinical Recommendations

When prescribing finasteride, physicians should:

• Inform patients about the 2-4% absolute increased risk of sexual dysfunction compared to placebo 1, 2
• Explain that these effects typically diminish with continued treatment 3
• Discuss the rare possibility of persistent sexual dysfunction that may continue after drug discontinuation 3
• Counsel patients that the magnitude of effect is relatively small compared to natural aging 1
• Instruct patients to promptly report any changes in sexual function 3

Mechanism

Finasteride inhibits the 5-alpha-reductase enzyme, which converts testosterone to dihydrotestosterone (DHT), potentially affecting sexual function through this hormonal pathway 2, 4