How to switch a patient from metoprolol 25 mg twice a day to propranolol?

Switching from Metoprolol 25 mg Twice Daily to Propranolol

For a patient on metoprolol 25 mg twice daily (50 mg total daily), switch directly to propranolol 80-120 mg daily in divided doses (40-60 mg twice daily), starting the propranolol the morning after the last metoprolol dose without any overlap or tapering period. 1

Dose Conversion Rationale

The ACC/AHA/ESC guidelines provide clear maintenance dosing for both agents in chronic therapy: metoprolol 25-100 mg twice daily and propranolol 80-240 mg daily in divided doses. 1 Since your patient is on the lowest therapeutic dose of metoprolol (25 mg twice daily = 50 mg total daily), the equivalent starting dose of propranolol should be at the lower end of the therapeutic range.

Recommended Conversion Strategy

• Start propranolol at 40 mg twice daily (80 mg total daily) as the initial conversion dose for a patient on metoprolol 25 mg twice daily. 1
• If additional rate control is needed after 3-5 days, increase to 60 mg twice daily (120 mg total daily). 1
• The maximum dose can reach 240 mg daily in divided doses if clinically indicated. 1

Timing of the Switch

• Discontinue metoprolol the evening before starting propranolol. 2
• Begin propranolol the following morning without any washout period or overlap. 2
• Unlike abrupt cessation without replacement, switching directly to another beta-blocker prevents withdrawal phenomena because continuous beta-blockade is maintained. 2

Why No Tapering is Needed

Research comparing withdrawal phenomena after different beta-blockers demonstrates that switching directly between beta-blockers does not produce the same withdrawal syndrome as complete cessation. 2 The key is maintaining some degree of beta-blockade during the transition. 3 Metoprolol has a relatively short half-life (3-7 hours), so by the next morning, plasma levels are minimal but propranolol provides immediate replacement beta-blockade. 2, 4

Critical Monitoring Parameters

First 48-72 Hours After Switch

• Check blood pressure and heart rate 2-4 hours after the first propranolol dose to assess for excessive beta-blockade or inadequate rate control. 1
• Monitor for symptomatic bradycardia (heart rate <60 bpm with dizziness or lightheadedness). 5
• Assess for hypotension (systolic BP <100 mmHg with symptoms like dizziness or lightheadedness). 5
• Listen for new or worsening bronchospasm, particularly if any history of reactive airway disease exists. 5

Ongoing Monitoring (First 2 Weeks)

• Recheck blood pressure and heart rate at 3-5 days and again at 1-2 weeks. 5
• Target resting heart rate should be 50-60 bpm unless limiting side effects occur. 5
• Watch for delayed adverse effects like fatigue or weakness, which may appear within 2-3 weeks. 5

Important Contraindications to Verify Before Switching

Both metoprolol and propranolol share the same major contraindications, but you must verify these are not present before making the switch:

• No signs of decompensated heart failure (new or worsening dyspnea, edema, orthopnea). 1
• No second or third-degree heart block without a functioning pacemaker. 1
• No active asthma or severe reactive airway disease. 1
• Systolic blood pressure >100 mmHg. 5
• Heart rate >50 bpm. 5

Propranolol-Specific Considerations

Dosing Schedule

• Propranolol must be given in divided doses (typically twice or three times daily) because it has a shorter half-life than metoprolol succinate extended-release. 1
• The onset of action is 60-90 minutes for oral propranolol. 1
• Administer propranolol with or after meals to enhance absorption and reduce risk of hypoglycemia. 1

Pharmacokinetic Differences

• Propranolol is a non-selective beta-blocker (blocks both β1 and β2 receptors), while metoprolol is β1-selective. 1
• This means propranolol has greater potential for bronchospasm in patients with any reactive airway component. 1
• Propranolol also has more CNS penetration and may cause more sleep disturbances or vivid dreams compared to metoprolol. 1

Common Pitfalls to Avoid

• Never stop metoprolol for several days before starting propranolol, as this creates a gap in beta-blockade and risks withdrawal phenomena including rebound hypertension, tachycardia, and angina exacerbation. 3, 2
• Do not use a 1:1 mg conversion ratio between metoprolol and propranolol—they are not equipotent on a milligram basis. 1
• Avoid starting propranolol at the maximum dose of 240 mg daily—begin at 80-120 mg daily and titrate up based on response. 1
• Do not overlook the need for divided dosing with propranolol—once-daily dosing is inadequate for sustained beta-blockade with immediate-release propranolol. 1, 6

Alternative Approach: Long-Acting Propranolol

If compliance with twice-daily dosing is a concern, consider long-acting propranolol formulation:

• Long-acting propranolol allows once-daily dosing with sustained beta-blockade over 24 hours. 6
• The bioavailability is 30-50% less than conventional propranolol, so doses may need to be higher. 6
• Start at 80 mg once daily of long-acting formulation, equivalent to approximately 40 mg twice daily of immediate-release. 6