What are the potential side effects of finasteride (Propecia) in men with benign prostatic hyperplasia (BPH) or androgenetic alopecia?

Finasteride Side Effects

Finasteride causes sexual side effects in approximately 6-10% of patients during the first year of treatment, with decreased libido (6.4%), erectile dysfunction (4-15%), and ejaculatory dysfunction (3.7%) being most common, and these effects typically decrease after the first year but may persist in a small subset of patients even after discontinuation. 1, 2, 3

Common Sexual Side Effects During Treatment

• Decreased libido occurs in 6.4% of patients in the first year, declining to 2.6% in years 2-4 2, 3
• Erectile dysfunction affects 4-15% of patients during treatment 3
• Ejaculatory dysfunction occurs in 3.7% in the first year, decreasing to 1.5% in years 2-4 2, 3
• These sexual side effects are reversible and become uncommon after the first year of therapy in most patients 1
• Sexual dysfunction was more pronounced with finasteride compared to placebo in the MTOPS trial, which prospectively measured erectile and ejaculatory function using validated questionnaires 1

Post-Finasteride Syndrome (Persistent Side Effects)

• The FDA amended finasteride labels to include warnings about persistent sexual dysfunction that may continue after drug discontinuation, including erectile dysfunction, decreased libido, ejaculation disorders, and orgasm disorders 1, 4
• Post-finasteride syndrome (PFS) is a controversial and poorly-defined constellation of sexual, physical, and psychological symptoms that putatively persist after discontinuation 1
• The robustness of data supporting PFS remains unclear, as it is based primarily on anecdotal patient-reported outcomes rather than prospective trials 1
• Reported persistent symptoms include sexual dysfunction, depression, anxiety, and cognitive complaints that remain present despite drug withdrawal 5, 6

Non-Sexual Side Effects

• Gynecomastia can occur with finasteride therapy 1
• Male breast cancer has been reported rarely in postmarketing surveillance, though the relationship between long-term finasteride use and male breast neoplasia is currently unknown 4
• Testicular pain and hematospermia have been reported in postmarketing experience 4
• Depression has been reported as an adverse event in postmarketing surveillance 4

Fertility and Reproductive Effects

• Male infertility and/or poor seminal quality were reported rarely in men taking finasteride for BPH 4
• Normalization or improvement of poor seminal quality has been reported after discontinuation of finasteride 4
• The independent role of finasteride in these fertility effects is unknown, as most men were older and taking concomitant medications 4

Prostate Cancer Considerations

• The incidence of high-grade Gleason score 8-10 prostate cancer was higher in men treated with finasteride (1.8%) compared to placebo (1.1%) in the 7-year PCPT trial 4
• This finding has been controversial, with some evidence suggesting delayed diagnosis due to lack of PSA adjustment (doubling the PSA value) rather than true increased cancer risk 1
• Patients taking finasteride who had delayed PSA adjustment were more likely to have higher-grade disease at diagnosis (25.2% vs 17.0% Gleason ≥8) 1

Critical Counseling Points

• Patients should be counseled that sexual side effects typically decrease after the first year but may persist in a small subset of individuals 1, 2
• The disadvantages of therapy, including sexual dysfunction, should be presented against the benefits of preventing disease progression (67% reduction in acute urinary retention and BPH-related surgery) 1, 2
• Finasteride reduces PSA by approximately 50% after 1 year of therapy, and measured PSA values should be doubled for accurate prostate cancer screening interpretation 2, 3
• Patients should not donate blood until 6 months after the last dose due to risk to pregnant females 7

Common Pitfalls to Avoid

• Using finasteride in patients without prostatic enlargement (<30cc) is ineffective and exposes patients to unnecessary side effects 1, 2
• Failing to adjust PSA interpretation (doubling the value after 1 year) can lead to delayed cancer diagnosis 1, 2
• Not allowing adequate time (at least 3-6 months) to assess finasteride's effectiveness before discontinuing 2, 3
• Dismissing patient concerns about persistent sexual side effects, as the FDA has acknowledged these may occur despite limited prospective data 1, 4