Alpha blockers are medications that block the effects of certain hormones in the body (e.g., the stress hormones). These stress hormones are closely related to the "fight or flight" response, and blocking them results in more relaxed arteries and a slower, more effective heartbeat. This has the effect of lowering blood pressure (the force of blood against artery walls). Certain alpha blockers have also been shown to favorably affect cholesterol levels.

However, alpha blockers have drawbacks, especially when compared to other antihypertensive medications. These drugs have relatively bothersome side effects, and large studies have shown that certain alpha blockers raise the risk of heart failure if used for the long-term.

The link between heart failure risk and alpha blocker use was found during the landmark ALLHAT study (Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial). ALLHAT also determined that other medications (e.g., diuretics) were preferred as first-line treatment for high blood pressure because they also lowered the risk of heart attack, stroke and other heart diseases without the side effects associated with alpha blockers.

Alpha blockers are sometimes used as part of a coordinated treatment of a blood pressure related condition called pheochromocytoma. However, their primary use is in the treatment of enlarged prostate. Specific types of alpha blockers or combined beta blockers may also be used in the treatment of peripheral vascular disease.

The side effects of alpha blockers may be intense after the first dose or within the first few days of taking the medication. Severe lowering of blood pressure may occur (especially after standing up) which may lead to dizziness or fainting (syncope). However, the side effects of alpha blockers tend to diminish with regular use.

Patients are generally directed to take alpha blockers at bedtime and increase doses gradually to decrease the risk of fainting. People are encouraged to call their physicians if they have any unusual symptoms while taking this medication, and physician’s orders about exercise, activity levels and diet should also be followed exactly.