Alpha Blockers are drugs that treat a variety of conditions, such as high blood pressure, benign prostatic hypertrophy (enlarged prostate) and Raynaud’s disease. They work by keeping the hormone norepinephrine (noradrenaline) from stimulating the muscles in the walls of smaller arteries and veins. This relaxes vessel walls and increases blood flow to the heart. (Also called alpha-adrenergic antagonists.)