Benign Prostatic Hyperplasia Medications

Two types of drugs are used to treat BPH: 5-alpha-reductase inhibitors and alpha-1-adrenergic blockers. Research suggests that these drugs improve symptoms in 30 to 60 percent of men. However, it is not yet possible to predict who will respond to medication or which drug will work best for a particular person.

5-alpha-reductase inhibitors

Two 5-alpha-reductase inhibitors are used to treat BPH: finasteride (Proscar) and dutasteride (Avodart). They inhibit the enzyme 5-alphareductase, which converts testosterone to dihydrotestosterone (DHT), the major male sex hormone within the cells of the prostate. The drugs work best in men with larger prostates—40 g (approximately 1.5 oz) or more—whose symptoms likely result from physical obstruction of the urethra.

The two 5-alpha-reductase inhibitors are equally effective. Both can reduce the size of the prostate by 20 to 30 percent, relieve BPH symptoms, and reduce the risk of acute urinary retention and the need for BPH surgery. However, these drugs must be continued indefinitely to prevent symptom recurrence. Moreover, it may take as long as a year to achieve maximal benefits.

Proscar and Avodart cause relatively few side effects. Erectile dysfunction, or ED (the inability to achieve a full erection), occurs in 5 to 8 percent of men, decreased libido (sex drive) in 3 to 6 percent, reduced ejaculate in 1 percent, and breast enlargement or tenderness in 0.5 percent. Sexual side effects tend to decrease with time, and they disappear when the drug is stopped. Breast-related side effects do not diminish with time but often improve once the drug is no longer taken.

Another side effect of both Proscar and Avodart is a lowering of PSA levels by about 50 percent. This can interfere with the results of PSA tests to detect prostate cancer if not taken into account. Men should have a PSA test before starting treatment with any 5-alpha-reductase inhibitor so that subsequent PSA values can be interpreted in light of this baseline value. If a man is already taking a 5-alpha-reductase inhibitor and no baseline PSA level was obtained, the results of his current PSA test should be doubled to estimate the true PSA level.

A PSA level that falls less than 50 percent after a year of treatment with a 5-alpha-reductase inhibitor suggests that the drug is not being taken as directed or that prostate cancer might be present. Similarly, an increase in PSA levels while taking a 5-alpha-reductase inhibitor suggests the possibility of prostate cancer. PSA values return to their true level after the 5-alpha-reductase inhibitor is stopped.

The medication Propecia—a lower dose of finasteride marketed for hair growth—also lowers a man's PSA value to the same extent as Proscar. Men who use Propecia should alert their physician so that their PSA results can be adjusted accordingly.

Alpha-1-adrenergic blockers (alpha-blockers)

These drugs relax smooth muscle tissue within the prostate by blocking the effect of nerve impulses that signal the muscles to contract. As a result, daily use of an alpha-blocker may increase urinary flow and relieve urinary frequency, urinary urgency, and frequent nighttime urination.

Currently, several alpha-blockers are used to treat BPH. These include alfuzosin (Uroxatral), doxazosin (Cardura), tamsulosin (Flomax), and terazosin (Hytrin). One advantage of alpha-blockers over 5-alpha-reductase inhibitors is that they work almost immediately. In addition, they can treat high blood pressure (hypertension) in men with that condition.

However, whether alpha-blockers are superior to 5-alpha-reductase inhibitors may depend more on the size of the prostate. In one comparison study, Hytrin appeared to produce greater improvement in BPH symptoms and urinary flow rate than Proscar. But this difference may have been due to the larger number of men with small prostates in the study. It is more likely that BPH symptoms in these men resulted from smooth muscle constriction rather than from physical obstruction by excess glandular tissue. Thus, they were more likely to respond to an alpha-blocker.

A review article published in The Journal of Urology found that all four alpha-blockers were effective at relieving BPH symptoms. Men taking Uroxatral had a 19 to 40 percent improvement in their symptom scores; those taking Cardura had a 14 to 39 percent improvement; men who were taking Flomax had a 24 to 50 percent improvement; and those taking Hytrin had a 38 to 64 percent improvement.

Men who have both BPH and an overactive bladder may benefit from treatment with an alpha-blocker and a drug used to treat incontinence, such as tolterodine (Detrol). In one study, men who took both Flomax and Detrol experienced greater improvements in their lower urinary tract symptoms than did men taking either medication alone.

Alpha-blockers can cause side effects such as orthostatic hypotension (dizziness upon standing due to a drop in blood pressure), fatigue, insomnia, and headache. These side effects are less common with Flomax because it does not lower blood pressure as much as the other alpha-blockers. Taking the drugs in the evening can minimize the risk of orthostatic hypotension.

Men who are taking alpha-blockers should be aware that these medications may interact with the oral phosphodiesterase type 5 (PDE5) inhibitors used to treat ED—sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra)—as the combination also can lead to hypotension. The recommendation is that Viagra not be taken within four hours of taking an alpha-blocker; that Levitra should not be used by anyone taking alpha-blockers; and that Cialis should be used only with Flomax at the 0.4-mg dose and not at all with the other alpha-blockers.

Among men taking blood pressure medication, alpha-blocker dosages may need to be adjusted to account for the drugs' blood pressure-lowering effects. Alpha-blockers may induce angina (chest pain resulting from an inadequate supply of oxygen to the heart) in men with coronary heart disease.

Men taking alpha-blockers who plan to undergo cataract surgery should tell their eye surgeon they are using the medication. Use of alpha-blockers has been found to make a man's iris more "floppy" during cataract surgery (a condition called floppy iris syndrome). However, the surgeon can adjust the surgical technique to avoid this problem if he or she is aware of the alpha-blocker use prior to the operation.

Publication Review By: H. Ballentine Carter, M.D.

Published: 10 Apr 2011

Last Modified: 31 Aug 2015