Beta-blockers are a class of drugs with complex cardiovascular effects, including reducing heart rate and oxygen demand in the heart muscle. Beta-blockers target beta receptors found in the different parts of the body, such as heart muscle, smooth muscles, blood vessels, airways, and kidneys. Beta-blockers work by inhibiting the release of neurotransmitters adrenaline and noradrenaline, which transmit signals from nerve endings to muscles, blood vessels, and the heart.

When are beta-blockers used?

• Angina - dull chest discomfort due to restricted blood supply to the heart muscle.
• Heart attack - sudden blockage of blood supply to a part of the heart muscle due to a blood clot.
• Heart failure - a situation where the heart is unable to pump the blood around the body adequately.
• Cardiac arrhythmias, including atrial fibrillation - fast and irregular heartbeat
• Hypertension - high blood pressure (140/90 mmHg or above)
  Less commonly, these agents are used in anxiety, overactive thyroid (thyrotoxicosis), glaucoma, and tremors.

Classification of beta-blockers

There are two types of beta-blockers: non-selective, i.e. without preference to any subtype of beta receptors (carvedilol, labetalol, propranolol, sotalol, and cardioselective, working mainly on heart tissue (atenolol, bisoprolol, metoprolol, nebivolol). Carvedilol, bisoprolol, and sustained-release metoprolol can be used in heart failure patients. 

Beta-blockers should not be stopped suddenly due to the risk of rebound phenomenon (sudden deterioration in symptoms).

Side effects

Beta-blockers are usually well tolerated, but the non-selective beta-blockers may have side effects, including dizziness and lightheadedness, fatigue, bradycardia (slow heartbeat), cold hands and feet. Beta-blockers are contraindicated in asthma.