Metoprolol

 Metoprolol – Full Introduction

Metoprolol is a β-adrenergic blocker (beta-blocker) that is cardioselective, meaning it primarily blocks β₁ receptors in the heart. It is widely used in the management of hypertension, angina pectoris, heart failure, and various cardiac arrhythmias. By reducing heart rate and cardiac output, metoprolol decreases the workload and oxygen demand of the heart.

Drug Class

• Beta-adrenergic blocker (β₁-selective)

Mechanism of Action

Metoprolol selectively blocks β₁-adrenergic receptors in the heart, leading to:

• Decreased heart rate (negative chronotropic effect)

• Decreased force of contraction (negative inotropic effect)

• Reduced cardiac output

• Suppression of renin release from the kidneys

These effects collectively lower blood pressure and reduce myocardial oxygen demand.

Therapeutic Uses

• Hypertension

• Angina pectoris

• Chronic heart failure (metoprolol succinate)

• Myocardial infarction (acute and post-MI)

• Supraventricular tachyarrhythmias

• Rate control in atrial fibrillation

Benefits

• Cardioselective (safer in asthma and diabetes than non-selective beta-blockers)

• Improves survival in heart failure and post-MI patients

• Effective heart rate control

• Available in immediate-release and extended-release forms

Common Side Effects

• Bradycardia

• Fatigue

• Dizziness

• Cold extremities

• Gastrointestinal discomfort

Serious but Rare Side Effects

• Severe bradycardia or heart block

• Hypotension

• Worsening of heart failure (initial phase)

• Bronchospasm (rare at high doses)

• Depression or sleep disturbances

Contraindications & Precautions

• Severe bradycardia

• Second- or third-degree heart block

• Cardiogenic shock

• Decompensated heart failure

• Use with caution in asthma, diabetes, and peripheral vascular disease

Conclusion

Metoprolol is a well-established, cardioselective beta-blocker with proven benefits in hypertension, ischemic heart disease, and heart failure. When used appropriately, it significantly improves cardiovascular outcomes and patient survival.