Overview

Beta blockers are a class of medicines that reduce the actions of the sympathetic nervous system on the heart and circulation. By blocking beta-adrenergic receptors they decrease heart rate, reduce force of contraction and can lower blood pressure, which lessens cardiac workload and oxygen demand.

Mechanism

These drugs interfere with the effects of stress hormones such as adrenaline and the related compound epinephrine, as well as the neurotransmitter noradrenaline, at beta receptors in the heart, lungs and blood vessels. Some agents selectively block beta-1 receptors (mainly cardiac), while nonselective agents also affect beta-2 receptors in bronchial and vascular smooth muscle.

Clinical uses

  • Treatment of hypertension and reduction of cardiovascular risk.
  • Rate control in atrial fibrillation and management of other arrhythmias.
  • Secondary prevention after myocardial infarction and for chronic stable angina.
  • Selected use in heart failure, migraine prevention, performance anxiety and certain endocrine conditions.

Drug selection and examples

Individual drugs differ in selectivity, lipophilicity and additional properties (for example, some combine beta and alpha blockade). Choice depends on the indication, comorbidities and side-effect profile; for instance, cardioselective agents are preferred when bronchospasm is a concern.

Side effects and precautions

Common adverse effects include fatigue, cold extremities and bradycardia. Nonselective agents can provoke bronchospasm and should be used with caution in people with asthma or reactive airways. Beta blockers may mask symptoms of hypoglycaemia in diabetes and can interact with other cardiovascular drugs; abrupt withdrawal may precipitate rebound sympathetic activity, so tapering is recommended.

Further information

Prescribing decisions follow clinical guidelines and individual assessment; for summaries and detailed reviews see therapeutic sources linked at class summaries and discussions of hormone interactions at adrenaline resources, receptor pharmacology at epinephrine/receptor, clinical reviews at noradrenaline references and practical guidance on blood-pressure management at hypertension guidance.