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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).
since prostate size does not always correspond to the severity of a man's
symptoms, these medicines will not give satisfactory results in every case.
When you stop taking the medicine, symptoms usually
Why It Is Used
5-alpha reductase inhibitors are not
recommended for men who have 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
American Urologic Association (AUA) symptom index.
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 6 to 12 months before symptom improvement is
Using a combination of an alpha-blocker with a
5-alpha reductase inhibitor may help your symptoms more than either medicine
Side effects may include:
- Decreased sex drive.
ejaculatory dysfunction (such as a smaller amount of semen
- Difficulty getting an erection.
tenderness or enlargement.
These side effects may go away after a year or more of taking the medicine.
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
5-alpha reductase inhibitors
reduce the size of the prostate. But since a reduction in size does not always
bring about symptom relief, these medicines will not give satisfactory results
in every case. When you stop taking the medicine, symptoms usually
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 exam)
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
- PSA levels above 2 ng/mL (nanograms per milliliter) during
5-alpha reductase inhibitor treatment may indicate a need for further testing
for prostate cancer.
5-alpha reductase inhibitors are not recommended for treatment of BPH symptoms
in men who do not have an enlarged prostate.1
The medicine must be taken for the rest of your life to prevent the
symptoms from returning.
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.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
AUA Practice Guidelines Committee (2003). AUA
guideline on management of benign prostatic hyperplasia (2003). Chapter 1:
Diagnosis and treatment recommendations. Journal of Urology, 170(2, Part 1): 530-547. Available online: http://www.auanet.org/content/guidelines-and-quality-care/clinical-guidelines.cfm?sub=bph.
Webber R (2006). Benign prostatic hyperplasia, search
date May 2005. Online version of BMJ Clinical Evidence.
Also available online: http://www.clinicalevidence.com.
Roehrborn CG, et al. (2008). The effects of
dutasteride, tamsulosin and combination therapy on lower urinary tract symptoms
in men with benign prostatic hyperplasia and prostatic enlargement: 2-year
results from the CombAT study. Journal of Urology,