Alpha-blocker medicines relax smooth muscle in the body. Smooth muscle controls the blood vessels, intestines, bladder and urinary tract, and other involuntary actions in the body.

Alpha-blockers can be used for many problems, including:

• Prostate problems. These medicines can relax the smooth muscle in the prostate and urethra, which lets urine flow out of the body more easily.
• Kidney stones. These medicines can relax the smooth muscle in the ureters (the tubes that move urine between the kidneys and the bladder) and make them wider, which can help a kidney stone pass more easily.
• High blood pressure. These medicines can relax the smooth muscle in the blood vessels and make them wider, which can help lower blood pressure.

Examples of alpha-blocker medicines include alfuzosin (Uroxatral), doxazosin (Cardura), silodosin (Rapaflo), tamsulosin (Flomax), and terazosin (Hytrin).

Side effects of alpha-blockers include:

• Dizziness, especially when standing up.
• Headache.
• Drowsiness.

Alpha-blockers are also called alpha-adrenergic antagonists.