Beta blockers are a class of drugs with complex cardiovascular effects including reduction in 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 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 - situation where heart is unable to adequate pump the blood around the body.
• Cardiac arrhythmias, including atrial fibrillation - fast and irregular heart beat
• 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

Beta blockers are non-selective, ie without preference to any subtype of beta receptors (carvedilol, labetalol, propranolol, sotalol) or 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 suddently due to the risk of rebound phenomenon (sudden deterioration in symptoms).

Side effects

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