A special concern for tamsulosin, and other selective alpha-blockers, is that they are associated with a condition called intraoperative floppy iris syndrome (IFIS). IFIS is a loss of muscle tone in the iris that can cause complications during cataract surgery. Patients who are planning cataract or other eye surgery should be sure to inform their doctors prior to the surgery. IFIS appears more likely to occur with selective alpha-blockers than non-selective alpha blockers.

5-Alpha-Reductase Inhibitors (5-ARIs)

The prostate gland contains an enzyme called 5 alpha-reductase that converts testosterone to another androgen called dihydrotestosterone. Finasteride (Proscar) and dutasteride (Avodart), known as 5-alpha-reductase inhibitors (5-ARIs), block this enzyme and thus reduce dihydrotestosterone in the prostate. This process helps to shrink an enlarged prostate and prevent future growth of the prostate. These drugs can also help prevent against urinary retention, and possibly reduce the need for future prostate surgery.

5-alpha-reductase inhibitors are not as effective as alpha-blockers in improving BPH and urinary tract symptoms, but they can help modestly reduce symptoms for some men. However, these drugs take several months before they have an effect so men may not notice any signs of improvement for 3 - 6 months. The 5 alpha-reductase inhibitors are most effective in reducing symptoms in men with large prostates.

Side Effects. The main side effects of finasteride and dutasteride are erectile dysfunction, lowered sexual drive (libido), and reduced semen release during ejaculation. These side effects generally subside within a year or two of treatment. (A positive side effect of finasteride is possible reduction of hair loss related to male hormones and, in some cases, hair growth in men with mild-to-moderate male pattern baldness.)

There is ongoing debate on whether 5-alpha-reductase inhibitors can help prevent prostate cancer in men who are at increased risk for this disease. The American Society of Clinical Oncology and American Urological Association recently issued guidelines concerning the pros and cons of 5-ARIs for prostate cancer prevention. Men who take these drugs for BPH should discuss this issue with their doctors. [For more information, see In-Depth Report #33: Prostate cancer.]

These drugs decrease prostate-specific antigen (PSA) levels, which may mask the presence of prostate cancer. To resolve this problem, doctors calculate PSA levels in men taking these drugs by doubling the PSA values. This doubling equation helps provide an accurate measurement.

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Review Date: 07/20/2010
Reviewed By: Harvey Simon, MD, Editor-in-Chief, Associate Professor of Medicine, Harvard Medical School; Physician, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org)