Beta blockers are drugs that block the effects of epinephrine and norepinephrine on specific
receptors, called beta receptors.
Beta
receptors are located in parts of the body including the heart,
arteries, and lungs. This group of drugs is used on patients with hypertension, irregular or rapid rhythms, heart attacks, and although counterintuitive, used with caution in patients with congestive heart failure.
Activation of beta receptors in the heart leads to increased rate and force of contraction, while in the arteries activated beta receptors contribute to an increase in blood pressure, and in the lungs, lead to dilation of bronchioles (small areas of gas exchange in the lungs). Beta blockers inhibit the response of these and other organs by slowing the heart rate and lowering the blood pressure. Propranolol, metoprolol, atelolol, and labetalol are examples of beta blockers. Side effects include hypotension, a slow heart rate, and wheezing or exacerbation of asthma.