5-alpha reductase inhibitors for benign prostatic hyperplasia

Examples

Generic Name	Brand Name
dutasteride	Avodart
finasteride	Proscar

How It Works

5-alpha reductase inhibitors interfere with the effect of certain male hormones (androgens) on the prostate. This slows the growth of the prostate and can even cause it to become smaller, which may help improve the symptoms of benign prostatic hyperplasia (BPH).

However, since prostate size does not always correspond to the severity of a man's symptoms, these medications will not give satisfactory results in every case.

When you stop taking the medication, symptoms usually return.

Why It Is Used

5-alpha reductase inhibitors are not recommended for men with BPH symptoms without a noticeably enlarged prostate. 5-alpha reductase inhibitors may be prescribed for men who have bothersome, moderate symptoms of BPH.

How Well It Works

Most men who use 5-alpha reductase inhibitors report about a 3-point decrease in their International Prostate Symptom Score (I-PSS). This change represents a noticeable improvement in symptoms.¹ 5-alpha reductase inhibitors also decrease the risk of complications, such as being unable to urinate (urinary retention), and make it less likely that you will need surgery.²

It may take up to 6 to 12 months before symptom improvement is noticeable.

Studies indicate that dutasteride is as effective as finasteride in reducing BPH symptoms.^{3, 4}

A U.S. National Institutes of Health (NIH) study found that combining finasteride (Proscar) with the alpha-blocker doxazosin (Cardura) reduces the chances of symptoms getting worse, urinary retention, and the need to have surgery. The combination of the two medicines worked better than either medicine alone or when compared with a placebo.⁵

Side Effects

5-alpha reductase inhibitors appear to be very safe and well-tolerated. Side effects found in the first year of use included:²

• Decreased sex drive.
• Increased ejaculatory dysfunction.
• Difficulty getting an erection.

However, one large study reported that after 1 year of treatment, finasteride resulted in the same level of decreased sex drive and inability to get an erection as a placebo. The risk for ejaculatory dysfunction was still increased with the use of finasteride.²

Initial studies on dutasteride report side effects of erection problems, decreased sex drive, breast tenderness and enlargement (rare), and ejaculation disorders.

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

What To Think About

5-alpha reductase inhibitors reduce the size of the prostate. However, since a reduction in size does not always bring about symptom relief, these medications will not give satisfactory results in every case. When you stop taking the medication, symptoms usually return.

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

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

5-alpha reductase inhibitors may be less effective than alpha-blockers in relieving symptoms.²

5-alpha reductase inhibitors are not recommended for treatment of BPH symptoms in men without an enlarged prostate.¹

The medication must be taken for the rest of your life to prevent the symptoms from returning.

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

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

Author:	Douglas Dana Ralph Poore	Last Updated: August 30, 2006
Medical Review:	Martin Gabica, MD - Family Medicine Adam Husney, MD - Family Medicine J. Curtis Nickel, MD, FRCSC - Urology Christopher G. Wood, MD, FACS - Urology/Oncology
© 1995-2008 Healthwise, Incorporated. Healthwise, Healthwise for every health decision, and the Healthwise logo are trademarks of Healthwise, Incorporated.This information does not replace the advice of a doctor. Healthwise disclaims any warranty or liability for your use of this information. Your use of this information means that you agree to the Terms of Use. How this information was developed to help you make better health decisions.