For men with moderate enlargement of the prostate and moderate urinary problems that are too bothersome not to treat, doctors often first prescribe an alpha blocker. Alpha blocker is shorthand for alpha-adrenergic–receptor antagonist, a class of medications that was originally approved to treat high blood pressure. Alpha blockers relax smooth muscle tissue by blocking the receptors that receive chemical signals “telling” the tissue to contract. In the prostate, this relaxation of smooth muscle means that the prostate’s “grip” on the urethra loosens, allowing urine to flow more freely.
Alpha blockers come in two forms: selective and nonselective.
Because the non- selective alpha blockers—doxazosin (Cardura), prazosin (Minipress), and terazosin (Hytrin)—can lower blood pressure, they may not be the best choice for men who are already taking a blood pressure medication. Taking several blood pressure medications at once can cause an excessive drop in blood pressure that makes people faint or get dizzy, especially when getting up from a chair or out of bed (orthostatic hypotension). Sudden episodes of low blood pressure can be dangerous for men with vascular disease, placing them at high risk for a heart attack or stroke.
By contrast, the selective alpha blockers (alfuzosin, silodosin, and tamsulosin) don’t lower blood pressure, making them useful for men who can’t tolerate blood pressure reduction.
Other side effects of alpha blockers include ankle swelling and retrograde ejaculation, when semen flows back into the bladder rather than out through the urethra.
Ejaculate volume is another issue with some alpha blockers. One study found that tamsulosin (Flomax) decreased ejaculate volume in almost 90% of men, while alfuzosin had no effect on ejaculate volume.
The difference between various alpha blockers is mainly in their side effects. Although there are few direct comparisons to go by, they seem equally effective in treating BPH and associated urinary symptoms. Moreover, the side effects vary more from man to man than they do from drug to drug, so there can be a fair amount of trial and error before an individual patient finds the right alpha blocker.