Beta blockers or beta-adrenergic blocking agents are a class of drugs used to treat a variety of cardiovascular conditions and some other diseases.

Beta blockers block the action of epinephrine and norepinephrine on the β-adrenergic receptors in the body (primarily in the heart, peripheral blood vessels, bronchi, pancreas, and liver). The hormones and neurotransmitters stimulate the sympathetic nervous system by acting on these receptors.

There are two types of beta receptors: β₁_receptors located mainly in the heart, and β₂_receptors located all over the body, but mainly in the lungs, muscles and arterioles.

Activition of β₁-receptors by epinephrine increases the heart rate and the blood pressure, and the heart consumes more oxygen. Drugs that block these receptors therefore have the reverse effect: they lower the heart rate and blood pressure and hence are used in conditions when the heart itself is deprived of oxygen. They are routinely prescribed in patients with ischemic heart disease. In addition, beta blockers prevent the release of renin, which is a hormone produced by the kidneys which leads to constriction of blood vessels.

Drugs that block beta 2 receptors generally have a relaxing effect and are prescribed for anxiety, migraine, esophageal varices and asthma or any reactive airway disease. Doing so can precipitate bronchospasm.

Since they lower heart rate, beta blockers have been abused by some Olympic marksmen to provide more aiming time between heartbeats.

Some musicians use beta blockers to avoid stage fright during auditions, and performances.

External link

• Musicians using beta blockers (http://www.sfgate.com/cgi-bin/article.cgi?file=/c/a/2004/10/17/MNGB599PJC1.DTL)