Beta-blockers

Beta-blockers (also written as β-blockers) are a class of medications that are primarily used to manage cardiovascular diseases. They work by blocking the effects of epinephrine (adrenaline) and norepinephrine (noradrenaline) on beta-adrenergic receptors, which are part of the sympathetic nervous system. This action helps to reduce heart rate, blood pressure, and the strain on the heart.

Medical uses

Beta-blockers are used in the treatment of various conditions, including:

• Hypertension (high blood pressure)
• Angina pectoris (chest pain)
• Heart failure
• Myocardial infarction (heart attack)
• Arrhythmias (irregular heartbeats)
• Anxiety disorders
• Migraine prophylaxis
• Glaucoma

Mechanism of action

Beta-blockers work by blocking the beta-adrenergic receptors in the heart and blood vessels. There are three main types of beta receptors: β1, β2, and β3. Most beta-blockers are selective for β1 receptors, which are primarily found in the heart. By blocking these receptors, beta-blockers reduce the effects of adrenaline and noradrenaline, leading to a decrease in heart rate and blood pressure.

Types of beta-blockers

Beta-blockers can be classified into two main categories:

• Non-selective beta-blockers: These block both β1 and β2 receptors. Examples include propranolol and nadolol.
• Selective beta-blockers: These primarily block β1 receptors. Examples include metoprolol, atenolol, and bisoprolol.

Side effects

Common side effects of beta-blockers include:

• Fatigue
• Cold extremities
• Bradycardia (slow heart rate)
• Hypotension (low blood pressure)
• Dizziness
• Depression
• Erectile dysfunction

Contraindications

Beta-blockers should be used with caution or avoided in certain conditions, such as:

• Asthma and chronic obstructive pulmonary disease (COPD)
• Severe peripheral artery disease
• Bradycardia
• Hypotension

History

Beta-blockers were first developed in the 1960s. The first clinically useful beta-blocker was propranolol, which was introduced by Sir James Black.

See also

• Adrenergic receptor
• Sympathetic nervous system
• Calcium channel blocker
• ACE inhibitor