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Beta Blockers: Classification, Uses, Adverse Effects, and Contraindications
Classification of Beta Blockers
- Non-selective Beta Blockers (Block β1 and β2 receptors): Propranolol, Nadolol, Timolol, Sotalol
- Cardioselective Beta Blockers (Primarily Block β1 receptors): Atenolol, Metoprolol, Bisoprolol, Esmolol
- Beta Blockers with Alpha-blocking Activity (Cause vasodilation): Labetalol, Carvedilol
- Beta Blockers with Intrinsic Sympathomimetic Activity (ISA): Pindolol, Acebutolol
- Ultra-short Acting Beta Blockers: Esmolol (used in acute situations due to its short half-life)
Therapeutic Uses of Beta Blockers
Cardiac Uses
- Hypertension: Lowers blood pressure by reducing cardiac output and renin release.
- Angina Pectoris: Reduces oxygen demand, relieving chest pain.
- Arrhythmias: Controls heart rate in conditions like atrial fibrillation.
- Heart Failure: Certain beta blockers improve survival by reducing cardiac workload.
- Myocardial Infarction (Post-MI): Decreases mortality by preventing arrhythmias.
Non-Cardiac Uses
- Migraine Prophylaxis: Reduces frequency of migraines (e.g., propranolol).
- Glaucoma: Lowers intraocular pressure (e.g., timolol eye drops).
- Hyperthyroidism and Thyroid Storm: Controls symptoms like tachycardia.
- Portal Hypertension: Reduces risk of esophageal variceal bleeding (e.g., propranolol).
- Pheochromocytoma: Used alongside alpha-blockers to control symptoms pre-surgery.
- Anxiety (Performance Anxiety): Reduces physical symptoms like tremors (e.g., propranolol).
- Essential Tremor: Provides relief by reducing tremor amplitude.
Adverse Effects of Beta Blockers
- Bradycardia
- Hypotension, causing dizziness and fainting
- Bronchospasm (especially with non-selective beta blockers)
- Fatigue and lethargy
- Cold extremities due to reduced blood flow
- Sexual dysfunction, including impotence
- Depression and sleep disturbances
- Hyperlipidemia (increase in triglycerides, decrease in HDL)
Contraindications of Beta Blockers
- Asthma or Severe COPD: Non-selective beta blockers can worsen bronchospasm.
- Bradycardia: Avoid in patients with abnormally low resting heart rate.
- Heart Block: Contraindicated in second- or third-degree AV block.
- Cardiogenic Shock or Decompensated Heart Failure: May further decrease cardiac output.
- Severe Peripheral Arterial Disease: Can worsen symptoms due to reduced circulation.
- Untreated Pheochromocytoma: Beta blockers should be avoided without alpha-blockade due to risk of hypertensive crisis.
