Dutasteride (Avodart) is FDA-approved for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate. At a dose of 0.5 mg once daily, dutasteride reduces prostate volume by a mean of 24.7% at 12 months, improving urinary symptoms, reducing the risk of acute urinary retention by 57%, and reducing the risk of BPH-related surgery by 48% compared to placebo.
What Is BPH?
Benign prostatic hyperplasia (BPH) is a non-cancerous enlargement of the prostate gland that commonly occurs in men as they age. The prostate surrounds the urethra, and when it enlarges, it can compress the urethra and obstruct urine flow. Prevalence rises steeply with age: histological BPH is found at autopsy in 50% to 60% of men in their 60s and in 80% to 90% of men older than 70.
Common symptoms of BPH include:
- Frequent urination, especially at night (nocturia)
- Weak or intermittent urine stream
- Difficulty starting urination (hesitancy)
- Feeling of incomplete bladder emptying
- Urgency to urinate
- Straining during urination
How Dutasteride Treats BPH
Dutasteride works by inhibiting both Type 1 and Type 2 5-alpha reductase enzymes, reducing the conversion of testosterone to DHT within the prostate gland. DHT is the primary androgen responsible for prostate growth. By reducing intraprostatic DHT levels, dutasteride causes apoptosis (cell death) in prostate tissue, gradually shrinking the gland and relieving urethral compression. Learn more about how dutasteride works.
Clinical Evidence for BPH
Dutasteride’s efficacy for BPH was established in three pivotal Phase III trials (ARIA3001, ARIA3002, and ARIB3003) involving over 4,300 men with moderate-to-severe BPH symptoms. Key findings at 24 months:
- Prostate volume: mean change of -26.7% on dutasteride vs -2.2% on placebo
- Maximum urine flow rate (Qmax): mean increase of 1.8 mL/sec on dutasteride vs 0.7 mL/sec on placebo
- AUA Symptom Index: mean decrease of 3.8 units on dutasteride vs 1.7 units on placebo
- Acute urinary retention: 1.8% on dutasteride vs 4.2% on placebo, a 57% reduction in risk
- BPH-related surgery: 2.2% on dutasteride vs 4.1% on placebo, a 48% reduction in risk
Dutasteride vs Tamsulosin for BPH
The CombAT (Combination of Avodart and Tamsulosin) trial compared dutasteride alone, tamsulosin alone, and combination therapy in 4,844 men with BPH over 4 years. Combination therapy (dutasteride + tamsulosin) was superior to either monotherapy for reducing the risk of BPH clinical progression, acute urinary retention, and BPH-related surgery. Read the full dutasteride vs tamsulosin comparison.
Dosage for BPH
The FDA-approved dose for BPH is 0.5 mg taken orally once daily. Dutasteride can be taken with or without food. Capsules should be swallowed whole, not crushed, chewed or opened. In the pivotal trials, symptom improvement reached statistical significance against placebo by Month 3 in one trial and by Month 12 in the other two, and dutasteride should be taken continuously to maintain its effects. Full dosage guide.
Side Effects in BPH Treatment
In the pivotal BPH trials, the most common side effects were sexual in nature: impotence (4.7% vs 1.7% placebo), decreased libido (3.0% vs 1.4%), ejaculation disorders (1.4% vs 0.5%), and breast disorders including breast tenderness and enlargement (0.5% vs 0.2%). Those are the rates reported in months 0 to 6, and each fell over the following 18 months of treatment. The label attaches an important qualifier to the sexual reactions: they may persist after treatment is discontinued, and dutasteride’s role in that persistence is unknown. Full side effects guide.
PSA Monitoring
Dutasteride reduces serum PSA (prostate-specific antigen) levels by approximately 50% within 3-6 months. When interpreting PSA results for prostate cancer screening, the PSA value should be doubled for comparison with normal values in untreated men. Any confirmed increase from the lowest PSA value recorded while on dutasteride should be evaluated for potential prostate cancer, even if the value is within the normal range for men not taking a 5-alpha reductase inhibitor.
Sources
- FDA. Avodart prescribing information. accessdata.fda.gov
- Roehrborn CG, Siami P, Barkin J, et al. The effects of combination therapy with dutasteride and tamsulosin on clinical outcomes in men with symptomatic benign prostatic hyperplasia: 4-year results from the CombAT study. Eur Urol. 2010;57(1):123-31. PubMed
- Roehrborn CG, Boyle P, Nickel JC, et al. Efficacy and safety of a dual inhibitor of 5-alpha-reductase types 1 and 2 (dutasteride) in men with benign prostatic hyperplasia. Urology. 2002;60(3):434-41. PubMed
- MedlinePlus. Dutasteride. medlineplus.gov
- FDA. Avodart (dutasteride) prescribing information, current label (supplement 032). accessdata.fda.gov
- StatPearls. Benign Prostatic Hyperplasia. ncbi.nlm.nih.gov