General Information

Proscar (finasteride) is a 5α-reductase inhibitor.

Proscar is specifically indicated for the treatment of symptomatic benign prostatic hyperplasia (BPH) in men with an enlarged prostate to:

Improve symptoms

Reduce the risk of acute urinary retention

Reduce the risk of the need for surgery including transurethral resection of the prostate (TURP) and prostatectomy.

Proscar is supplied as tablets. Proscar may be administered with or without meals.

Monotherapy: One tablet (5 mg) taken once a day

Combination with Doxazosin: One tablet (5 mg) taken once a day in combination with the alpha-blocker doxazosin

Mechanism of Action

Proscar (finasteride) is a 5α-reductase inhibitor. The development and enlargement of the prostate gland is dependent on the potent androgen, 5α-dihydrotestosterone (DHT). Type II 5α-reductase metabolizes testosterone to DHT in the prostate gland, liver and skin. DHT induces androgenic effects by binding to androgen receptors in the cell nuclei of these organs. Finasteride is a competitive and specific inhibitor of Type II 5α-reductase with which it slowly forms a stable enzyme complex. Turnover from this complex is extremely slow (t½  30 days). This has been demonstrated both in vivo and in vitro. Finasteride has no affinity for the androgen receptor. In man, the 5α-reduced steroid metabolites in blood and urine are decreased after administration of finasteride.

Clinical Trial Results

Proscar 5 mg/day was initially evaluated in patients with symptoms of BPH and enlarged prostates by digital rectal examination in two 1-year, placebo-controlled, randomized, double-blind studies and their 5-year open extensions. Proscar was further evaluated in the Proscar Long-Term Efficacy and Safety Study (PLESS), a double-blind, randomized, placebo-controlled, 4-year, multicenter study. 3040 patients between the ages of 45 and 78, with moderate to severe symptoms of BPH and an enlarged prostate upon digital rectal examination, were randomized into the study (1524 to finasteride, 1516 to placebo) and 3016 patients were evaluable for efficacy. 1883 patients completed the 4-year study (1000 in the finasteride group, 883 in the placebo group). Effect on Symptom Score Symptoms were quantified using a score similar to the American Urological Association Symptom Score, which evaluated both obstructive symptoms (impairment of size and force of stream, sensation of incomplete bladder emptying, delayed or interrupted urination) and irritative symptoms (nocturia, daytime frequency, need to strain or push the flow of urine) by rating on a 0 to 5 scale for six symptoms and a 0 to 4 scale for one symptom, for a total possible score of 34. Patients in PLESS had moderate to severe symptoms at baseline (mean of approximately 15 points on a 0-34 point scale). Patients randomized to Proscar who remained on therapy for 4 years had a mean decrease in symptom score of 3.3 points compared with 1.3 points in the placebo group. A statistically significant improvement in symptom score was evident at 1 year in patients treated with Proscar vs placebo (–2.3 vs –1.6), and this improvement continued through Year 4.