Beta-adrenergic antagonist

Beta-Adrenergic Antagonist

Beta-adrenergic antagonists, commonly known as beta blockers, are a class of medications that are primarily used to manage abnormal heart rhythms, protect the heart from a second heart attack after a first heart attack (secondary prevention), and treat hypertension. They work by blocking the effects of the hormone epinephrine, also known as adrenaline, on the beta receptors of the heart and other parts of the body.

Mechanism of Action

Beta blockers exert their effects by blocking the beta-adrenergic receptors, which are part of the sympathetic nervous system. There are three main types of beta receptors: β1, β2, and β3.

• β1 receptors are primarily located in the heart and kidneys. Blocking these receptors leads to a decrease in heart rate, cardiac output, and renin release from the kidneys.
• β2 receptors are found in the lungs, gastrointestinal tract, liver, uterus, vascular smooth muscle, and skeletal muscle. Blocking these receptors can lead to bronchoconstriction and vasoconstriction.
• β3 receptors are involved in the regulation of lipolysis and thermogenesis.

Clinical Uses

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

• Hypertension
• Angina pectoris
• Myocardial infarction (heart attack)
• Heart failure
• Arrhythmias, such as atrial fibrillation
• Migraine prophylaxis
• Anxiety

Common Beta Blockers

Some commonly prescribed beta blockers include:

• Propranolol - a non-selective beta blocker used for hypertension, anxiety, and migraine prophylaxis.
• Metoprolol - a selective β1 blocker used for hypertension, angina, and heart failure.
• Atenolol - a selective β1 blocker used for hypertension and angina.
• Carvedilol - a non-selective beta blocker with alpha-blocking activity, used for heart failure and hypertension.
• Bisoprolol - a selective β1 blocker used for hypertension and heart failure.

Side Effects

Common side effects of beta blockers include:

• Fatigue
• Cold hands and feet
• Weight gain
• Depression
• Bradycardia (slow heart rate)
• Hypotension (low blood pressure)

Contraindications

Beta blockers are contraindicated in patients with:

• Asthma or severe chronic obstructive pulmonary disease (COPD)
• Severe bradycardia
• Second or third-degree heart block
• Cardiogenic shock

See Also

• Adrenergic receptor
• Sympathetic nervous system
• Hypertension management