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5-Alpha Reductase Inhibitors for Prostatitis


Generic Name Brand Name
dutasteride Avodart
finasteride Proscar

How It Works

5-alpha reductase inhibitors interfere with the effect of male hormones (androgens) on the prostate gland, which cause the prostate to become larger. This stops the growth of the prostate and can even cause it to become smaller. Stopping the growth of the prostate or reducing its size may help relieve pain or urination problems caused by prostatitis.

Why It Is Used

5-alpha reductase inhibitors may be prescribed for men who have prostatitis (especially chronic prostatitis/pelvic pain syndrome, inflammatory) and who also have moderate symptoms of prostate enlargement.

How Well It Works

Some studies have shown that finasteride can help with symptoms of prostatitis. But in other studies, finasteride didn't improve symptoms any more than placebo.1

Dutasteride has also been shown to improve symptoms of prostatitis.2

Side Effects

Side effects may include:

  • Decreased sex drive.
  • Reduced ejaculatory volume.
  • Difficulty getting an erection.
  • Breast tenderness or enlargement.

It is possible that 5-alpha reductase inhibitors are linked to an increased risk for high-grade prostate cancers. But more research is needed.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

This medicine should not be used by men who plan to father a child, because there is a small chance that the medicine could cause a birth defect. Women who are pregnant or might become pregnant should not handle broken or crushed tablets of finasteride or dutasteride.

5-alpha reductase inhibitors reduce prostate-specific antigen (PSA) levels. Because PSA levels are used to detect early-stage prostate cancer, men interested in taking 5-alpha reductase inhibitors might consider the following:

  • Some experts suggest that men be checked for the presence of prostate cancer (using the PSA test and a digital rectal exam) before starting to take 5-alpha reductase inhibitors.
  • Follow-up PSA tests that have not decreased by approximately 50% after 6 months of taking 5-alpha reductase inhibitors may point to a need for further testing for prostate cancer.
  • PSA levels above 2 ng/mL during 5-alpha reductase inhibitor treatment may point to a need for further testing for prostate cancer.

Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.


  1. Nickel JC (2012). Prostatitis and related conditions, orchitis, and epididymitis. In AJ Wein et al., eds., Campbell-Walsh Urology, 10th ed., vol. 1, pp. 327–356. Philadelphia: Saunders.

  2. Nickel JC, et al. (2011). Dutasteride reduces prostatitis symptoms compared with placebo in men enrolled in the REDUCE study. Journal of Urology, 186(4): 1313–1318.

By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Christopher G. Wood, MD, FACS - Urology, Oncology
Current as of November 11, 2013

WebMD Medical Reference from Healthwise

Last Updated: November 11, 2013
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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