What is the average reduction in prostate volume achieved by 5-alpha-reductase inhibitors (5-ARIs) like finasteride (generic) and dutasteride (generic) in the treatment of benign prostatic hyperplasia (BPH)?

From the Guidelines

5-alpha-reductase inhibitors (5-ARIs) like finasteride and dutasteride typically reduce prostate volume by approximately 15-25% in men with benign prostatic hyperplasia (BPH). This reduction occurs gradually over 3-6 months of treatment, with maximum effects usually seen after 6-12 months of continuous therapy 1. Finasteride (5mg daily) and dutasteride (0.5mg daily) work by blocking the conversion of testosterone to dihydrotestosterone (DHT), the hormone primarily responsible for prostate growth. Dutasteride inhibits both type 1 and type 2 5-alpha-reductase enzymes, while finasteride blocks only type 2, which may explain why some studies suggest dutasteride produces slightly greater volume reductions.

Key Points

• The decrease in prostate size leads to improved urinary flow rates and symptom relief for many patients, though these medications may take several months to show noticeable benefits.
• Side effects can include sexual dysfunction (reduced libido, erectile dysfunction), ejaculatory disorders, and rarely gynecomastia.
• These medications are most effective in men with larger prostates (>30cc) and should be continued long-term as discontinuation typically results in prostate regrowth to pre-treatment size within 6-12 months.
• The most recent and highest quality study suggests that 5-ARIs can reduce prostate volume by 15-25% at six months, with a significant reduction in androgenic growth and an increase in apoptosis and atrophy 1. Some key considerations for the use of 5-ARIs in BPH treatment include:
• Patient selection: 5-ARIs are most effective in men with larger prostates (>30cc) and higher PSA values (>1.5ng/mL).
• Combination therapy: 5-ARIs can be used in combination with alpha blockers to maximize symptom control.
• Monitoring: Patients on 5-ARIs should be monitored for changes in PSA levels and prostate volume, as well as for potential side effects. Overall, 5-ARIs are a effective treatment option for men with BPH, particularly those with larger prostates and higher PSA values. By reducing prostate volume and improving urinary flow rates, 5-ARIs can significantly improve the quality of life for men with BPH 1.

From the FDA Drug Label

At Month 12, the mean percent change in prostate volume across the 3 trials pooled was -24.7% for dutasteride and -3.4% for placebo; the mean difference (dutasteride minus placebo) was -21.3% (range: -21% to -21.6% in each of the 3 trials, P <0.001). At Month 24, the mean percent change in prostate volume across the 3 trials pooled was -26.7% for dutasteride and -2.2% for placebo with a mean difference of -24.5% (range: -24% to -25.1% in each of the 3 trials, P <0.001).

The average reduction in prostate volume achieved by dutasteride is -26.7% at Month 24, with a mean difference of -24.5% compared to placebo 2.

• The reduction in prostate volume is statistically significant, with p-values < 0.001.
• The mean percent change in prostate volume for dutasteride at Month 12 is -24.7%.
• The mean percent change in prostate volume for dutasteride at Month 24 is -26.7%.

From the Research

Reduction in Prostate Volume

The average reduction in prostate volume achieved by 5-alpha-reductase inhibitors (5-ARIs) like finasteride and dutasteride in the treatment of benign prostatic hyperplasia (BPH) is:

• 20-25% after 6 months of therapy with finasteride, as reported in a study published in 1998 3
• 23.3% after 12 months of therapy with finasteride, as reported in a study published in 1997 4
• 25% after 2 years of therapy with dutasteride, as reported in a study published in 2008 5

Comparison of Finasteride and Dutasteride

Both finasteride and dutasteride have been shown to decrease prostate volume, improve lower urinary tract symptoms (LUTS), and increase urinary flow rates:

• Finasteride reduces serum 5 alpha-dihydrotestosterone (5 alpha-DHT) levels by approximately 80% 3
• Dutasteride reduces serum prostate-specific antigen levels by approximately 50% at 6 months and total prostate volume by 25% after 2 years 5

Clinical Significance

The reduction in prostate volume achieved by 5-ARIs can lead to:

• Improved LUTS and urinary flow rates 6
• Reduced risk of acute urinary retention and the need for surgical treatment 7
• Decreased incidence of prostate cancer, although the clinical significance of this is still debated 5