The effect of finasteride in men with benign prostatic hyperplasia. The Finasteride Study Group

N Engl J Med. 1992 Oct 22;327(17):1185-91. doi: 10.1056/NEJM199210223271701.


Background: Benign prostatic hyperplasia is a progressive, androgen-dependent disease resulting in enlargement of the prostate gland and urinary obstruction. Preventing the conversion of testosterone to its tissue-active form, dihydrotestosterone, by inhibiting the enzyme 5 alpha-reductase could decrease the action of androgens in their target tissues; in the prostate the result might be a decrease in prostatic hyperplasia and therefore in symptoms of urinary obstruction.

Methods: In a double-blind study, we evaluated the effect of two doses of finasteride (1 mg and 5 mg) and placebo, each given once daily for 12 months, in 895 men with prostatic hyperplasia. Urinary symptoms, urinary flow, prostatic volume, and serum concentrations of dihydrotestosterone and prostate-specific antigen were determined periodically during the treatment period.

Results: As compared with the men in the placebo group, the men treated with 5 mg of finasteride per day had a significant decrease in total urinary-symptom scores (P less than 0.001), an increase of 1.6 ml per second (22 percent, P less than 0.001) in the maximal urinary-flow rate, and a 19 percent decrease in prostatic volume (P less than 0.001). The men treated with 1 mg of finasteride per day did not have a significant decrease in total urinary-symptom scores, but had an increase of 1.4 ml per second (23 percent) in the maximal urinary-flow rate, and an 18 percent decrease in prostatic volume. The men given placebo had no changes in total urinary-symptom scores, an increase of 0.2 ml per second (8 percent) in the maximal urinary-flow rate, and a 3 percent decrease in prostatic volume. The frequency of adverse effects in the three groups was similar, except for a higher incidence of decreased libido, impotence, and ejaculatory disorders in the finasteride-treated groups.

Conclusions: The treatment of benign prostatic hyperplasia with 5 mg of finasteride per day results in a significant decrease in symptoms of obstruction, an increase in urinary flow, and a decrease in prostatic volume, but at a slightly increased risk of sexual dysfunction.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • 5-alpha Reductase Inhibitors*
  • Adult
  • Aged
  • Androstenes / administration & dosage
  • Androstenes / adverse effects
  • Androstenes / therapeutic use*
  • Azasteroids / administration & dosage
  • Azasteroids / adverse effects
  • Azasteroids / therapeutic use*
  • Dihydrotestosterone / blood
  • Double-Blind Method
  • Erectile Dysfunction / etiology
  • Finasteride
  • Humans
  • Male
  • Middle Aged
  • Prostate / pathology
  • Prostate-Specific Antigen / analysis
  • Prostatic Hyperplasia / complications
  • Prostatic Hyperplasia / drug therapy*
  • Prostatic Hyperplasia / physiopathology
  • Urodynamics


  • 5-alpha Reductase Inhibitors
  • Androstenes
  • Azasteroids
  • Dihydrotestosterone
  • Finasteride
  • Prostate-Specific Antigen