Equivalent Beta Blocker Dosing for Propranolol 40 mg BID
For a patient on propranolol 40 mg twice daily (80 mg total daily), switch to metoprolol succinate 100 mg once daily as the equivalent dose. 1, 2
Conversion Rationale
The conversion from propranolol to metoprolol is based on relative beta-blocking potency and clinical equivalence:
- Propranolol 80 mg daily (40 mg BID) converts to approximately metoprolol succinate 100-200 mg once daily 1, 2
- The American College of Cardiology recommends metoprolol as a preferred alternative to propranolol due to proven mortality benefits, particularly in patients with cardiovascular conditions 2
- Metoprolol succinate (extended-release) provides consistent beta-blockade over 24 hours with once-daily dosing, avoiding the peaks and troughs seen with immediate-release formulations 3
Recommended Switching Protocol
Never abruptly discontinue propranolol - this can cause severe exacerbation of angina, myocardial infarction, ventricular arrhythmias, and carries a 50% mortality rate in some studies 2
Step-by-Step Transition:
- Taper propranolol over 1-2 weeks by reducing the dose by 25-50% every few days 2
- Initiate metoprolol succinate at 50-100 mg once daily on the day after the last propranolol dose 1, 2
- Monitor blood pressure and heart rate during the transition period 2
- Titrate metoprolol to target dose of 100-200 mg daily based on clinical response over 1-2 weeks 1
Alternative Beta Blocker Options
If metoprolol is not suitable, consider these alternatives based on clinical context:
- Bisoprolol: Highly cardioselective, once-daily dosing, proven mortality benefit in heart failure 2
- Carvedilol: Combined alpha- and beta-blocking properties, particularly beneficial in heart failure patients 2
- Atenolol: Beta-1 selective, once-daily dosing, though less preferred than metoprolol or bisoprolol 2
For patients with reactive airway disease or COPD, choose beta-1 selective agents (metoprolol, bisoprolol, atenolol, or nebivolol) and use cautiously with low initial doses 2
Contraindications to Verify Before Switching
Confirm absence of the following before initiating any beta blocker:
- Second or third-degree AV block without a functioning pacemaker 1, 2
- Decompensated heart failure or cardiogenic shock 1, 2
- Severe bradycardia (heart rate <50 bpm with symptoms) 1
- Systolic blood pressure <100 mmHg with symptoms 1
- Active asthma or severe reactive airway disease 1, 2
Monitoring Parameters Post-Switch
- Check blood pressure and heart rate within 1-2 weeks after switching 2
- Target resting heart rate of 50-60 beats per minute unless limiting side effects occur 1
- Monitor for signs of worsening heart failure (increased dyspnea, fatigue, edema, weight gain) 1
- Watch for hypotension, bradycardia, and bronchospasm as common adverse effects 1
Critical Drug Interactions
Avoid routine combination with non-dihydropyridine calcium channel blockers (diltiazem, verapamil) due to increased risk of severe bradycardia and heart block 2
Dosing Equivalence Summary
| Propranolol | Metoprolol Succinate (ER) | Metoprolol Tartrate (IR) |
|---|---|---|
| 80 mg daily (40 mg BID) | 100-200 mg once daily | 50-100 mg twice daily |
The extended-release metoprolol succinate formulation is strongly preferred over immediate-release metoprolol tartrate for once-daily dosing and consistent 24-hour beta-blockade 1, 3