When compared with placebo and other drugs, long-term use of finasteride improves urinary tract symptoms associated with benign prostatic hyperplasia, and reduces disease progression. This conclusion comes from combining the findings of 23 randomized clinical trials that evaluated almost 21,000 men, and is published this month in The Cochrane Library.

Finasteride is frequently given to men who have lower urinary tract symptoms (LUTS) such as frequent voiding at night (nocturia), incomplete emptying, hesitancy, weak stream, and frequent and urgent urination. The symptoms are often caused by prostatic smooth-muscle contractions, and by benign prostatic hyperplasia, a non-cancerous condition in which the prostate gland grows too large.

Like many organs in the body, the size of the prostate is influenced by particular hormones. Dihydrotestosterone is one hormone that increases its size. Finasteride belongs to a class of drugs called 5 alpha reductase inhibitors (5ARI) that reduce prostate size. The full effects of how 5ARIs shrink the prostate are not fully understood, but in part they work by blocking the body's ability to make dihydrotestosterone.

Pharmacologic therapy is the most frequent way of treating men with moderate to severe LUTS and related symptoms. Drugs like finasteride are frequently prescribed to improve LUTS and reduce long-term symptom progression, including the risk for acute urinary retention and the need for surgical intervention. "We needed to determine the effectiveness and harms of finasteride when used on its own or in combination with other therapies, and to compare this with similar drugs," says study leader James Tacklind, who works at the Veterans Affairs Medical Center, Minneapolis, USA.

Finasteride was even more effective at lowering symptom scores when used in combination with doxazosin, an alpha blocker.

"Finasteride seems to be more effective in men with large prostates who use the drugs for at least 1 year, compared to those with small prostates," says Tacklind.

Looking at drug-related adverse effects, the researchers found that they were uncommon in men using finasteride; nevertheless, compared to placebo, men taking it are at slightly increased risk for impotence, erectile dysfunction, decreased libido, and ejaculation disorder.