From the Guidelines
Approximately 50% of men experience erectile dysfunction (ED) as a side effect of finasteride, according to the Prostate Cancer Prevention Trial (PCPT) study 1. Finasteride, commonly prescribed at 1mg daily for male pattern baldness (Propecia) or 5mg daily for benign prostatic hyperplasia (Proscar), works by inhibiting the enzyme 5-alpha-reductase, which converts testosterone to dihydrotestosterone (DHT). While this reduction in DHT helps treat hair loss and prostate enlargement, it can also affect sexual function in some men. The risk of ED appears to be dose-dependent, with higher doses carrying a slightly greater risk. Some key points to consider:
- The PCPT study found that 67.4% of men taking finasteride experienced ED, compared to 61.5% of men taking a placebo 1.
- Other studies have reported varying rates of ED associated with finasteride, ranging from 4.2% to 15.8% 1.
- Most sexual side effects, including ED, typically resolve after discontinuing the medication, though in rare cases, some men report persistent sexual dysfunction even after stopping finasteride.
- If you experience ED while taking finasteride, consult your healthcare provider, as they may recommend reducing the dose, stopping the medication, or trying alternative treatments.
- The mechanism behind finasteride-induced ED likely involves hormonal changes affecting nitric oxide pathways necessary for normal erections, though the exact process isn't fully understood.
From the FDA Drug Label
The incidence rates of drug-related adverse experiences reported by ≥2% of patients in any treatment group in the MTOPS Study are listed in Table 2 ... Urogenital ... Impotence 12.2 14.4 18.5 22.6
The percentage of men who experience erectile dysfunction (impotence) with finasteride is 18.5% 2.
From the Research
Erectile Dysfunction with Finasteride
- The percentage of men experiencing erectile dysfunction with finasteride varies across studies, with some reporting a higher incidence of sexual side effects, including erectile dysfunction, loss of libido, and ejaculation disorders 3.
- A study found that 15% of men experienced sexual adverse effects, including erectile dysfunction, after 1 year of finasteride therapy 3.
- Another study reported that 20% of subjects with male pattern hair loss experienced persistent sexual dysfunction, including erectile dysfunction, for ≥6 years despite discontinuation of finasteride 4.
- A review of current research studies on finasteride-associated erectile dysfunction found that most studies correlated finasteride use for benign prostatic hyperplasia with erectile dysfunction, but not for male androgenetic alopecia 5.
- The risk of persistent erectile dysfunction was found to be higher in men with longer exposure to 5α-reductase inhibitors, including finasteride, with 1.4% of men developing persistent erectile dysfunction after finasteride exposure 6.
- The incidence of erectile dysfunction was reported to be 9.6% in one study, with a significant higher proportion of sexual side effects reported by patients informed about potential sexual side effects of finasteride 3.
Factors Influencing Erectile Dysfunction with Finasteride
- Duration of finasteride exposure was found to be a significant predictor of persistent erectile dysfunction, with longer exposure increasing the risk of erectile dysfunction 6.
- Age and prostate disease were also found to be significant predictors of persistent erectile dysfunction in men taking finasteride 6.
- The use of nonsteroidal anti-inflammatory drugs (NSAIDs) was found to increase the risk of persistent erectile dysfunction in men taking finasteride 6.
- The nocebo effect, where patients experience adverse effects due to their expectations of side effects, was found to play a significant role in the reporting of sexual side effects, including erectile dysfunction, in men taking finasteride 3.