Harvard Men's Health Watch

On call: How urinary drugs affect blood pressure

Q. I recently started using an alpha blocker to relieve my difficulties starting urination and emptying my bladder. I am concerned about the drug's known tendency to lower blood pressure, since mine is already on the low side. Is this medication safe to take?

A. You can use these medications safely if you are aware of the side effects and report any problems to your doctor so adjustments can be made. Alpha blockers vary in their effects on blood pressure. The medications relax the muscles in the prostate gland to allow easier emptying of the bladder. But the medication also relaxes muscles in blood vessels, which makes blood pressure drop.

The effect varies according to the drug you take. The alpha blockers tamsulosin (Flomax) and silodosin (Rapaflo) affect blood pressure very little, although a few men still say they feel dizzy. Older alpha blockers, such as terazosin (Hytrin) and doxazosin (Cardura), can have a more pronounced effect and may cause fainting, although this happens to only about 1% of men. The effect on blood pressure of the alpha blocker Alfuzosin (Uroxatral) lies somewhere between the two extremes.

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