What are the differences between metoprolol (beta-blocker) and propranolol (beta-blocker) in terms of usage and dosage?

Differences Between Metoprolol and Propranolol: Usage and Dosage

Metoprolol is a cardioselective beta-blocker that preferentially blocks beta-1 receptors at lower doses, while propranolol is a non-selective beta-blocker that blocks both beta-1 and beta-2 receptors, making metoprolol generally preferred in patients with respiratory conditions. 1

Key Differences in Selectivity and Clinical Applications

Receptor Selectivity

• Metoprolol is a beta-1 selective (cardioselective) adrenergic receptor blocker, though this selectivity is not absolute and diminishes at higher doses 2
• Propranolol is non-selective, blocking both beta-1 and beta-2 receptors, affecting both cardiac tissue and bronchial/vascular smooth muscle 1

Respiratory Considerations

• Metoprolol is preferred in patients with bronchospastic airway disease requiring beta blockade due to its relative beta-1 selectivity 1
• Propranolol should be avoided in patients with reactive airways disease due to its non-selective nature and greater risk of bronchospasm 1, 3
• In hypertensive patients with asthma, metoprolol causes less bronchospasm than propranolol, but should still be used cautiously and at lower doses (not exceeding 100mg daily) 4

Dosing Regimens

Metoprolol

• Metoprolol tartrate: 100-200 mg daily in 2 divided doses 1
• Metoprolol succinate (extended-release): 50-200 mg once daily 1, 5
• Initial dosing for hypertension: 25-50 mg twice daily for tartrate; 50-100 mg once daily for succinate 5

Propranolol

• Propranolol immediate release (IR): 80-160 mg daily in 2 divided doses 1
• Propranolol long-acting (LA): 80-160 mg once daily 1

Clinical Efficacy Comparisons

Hypertension

• Metoprolol may produce greater reductions in blood pressure compared to propranolol at equipotent doses (327 mg metoprolol vs. 282 mg propranolol daily) 6
• In a long-term study, metoprolol showed significantly greater reductions in supine diastolic and standing systolic blood pressures compared to propranolol 6

Angina Pectoris

• Both drugs are equally effective in relieving angina pectoris and increasing exercise tolerance 7
• Mean increase in exercise tolerance with metoprolol was approximately 36% in comparative studies 7

Special Considerations and Precautions

Heart Failure

• Bisoprolol and metoprolol succinate are preferred in patients with heart failure with reduced ejection fraction (HFrEF) 1
• Carvedilol is also preferred in HFrEF patients 1
• Propranolol is not specifically indicated for heart failure management 1

Abrupt Discontinuation

• Both medications require gradual tapering to avoid rebound hypertension, worsening angina, or potential cardiac events 1, 2
• For metoprolol, tapering should reduce dose by 25-50% every 1-2 weeks 5

Contraindications for Both Drugs

• Marked first-degree AV block (PR interval >0.24 seconds) 1, 2
• Second or third-degree heart block without a pacemaker 1, 2
• Cardiogenic shock or decompensated heart failure 1, 2

Practical Prescribing Considerations

• For patients requiring beta blockade who also have asthma or COPD, metoprolol is the safer choice, but should be used at the lowest effective dose 3, 4
• For patients with no respiratory concerns, either drug can be effective for hypertension or angina, though metoprolol may offer better blood pressure control 6
• When using metoprolol in patients with bronchospastic disease, consider administering in smaller doses three times daily rather than larger doses twice daily to minimize peak plasma levels 2

Monitoring Parameters

• Blood pressure and heart rate should be monitored regularly with both medications 5
• In patients with asthma or COPD, respiratory function should be closely monitored, particularly when initiating therapy or increasing doses 3, 4
• Signs of worsening heart failure should be monitored with both agents 2