beta-blocker

n. A drug which blocks beta-adrenergic receptors, which are found in the central nervous system, the sympathetic nervous system, the heart, and other organs. Beta-adrenergic receptors are a type of adrenaline- (epinephrine-) sensitive receptor sites. Treatment with a beta-blocker decreases the rate and force of heart muscle contraction and decreases sympathetic nervous system activity. The former action is useful to treat tachycardia (rapid heart rate) and/or high blood pressure, arrhythmias, and angina. The latter action of a beta-blocker is useful in treating people with excessive startle responses or with stage fright. The prototypic beta-blocker is propranolol, though many other beta-blockers are available for specific uses.

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