What is the appropriate starting dose and titration of metoprolol (beta-blocker) for managing conditions like paroxysmal atrial fibrillation or hypertension?

Metoprolol Dosing for Paroxysmal Atrial Fibrillation and Hypertension

For paroxysmal atrial fibrillation and hypertension, the appropriate initial dose of metoprolol tartrate is 25-50 mg twice daily, with gradual titration to a maximum of 200 mg daily; for metoprolol succinate (extended-release), start with 50 mg once daily and titrate up to a maximum of 400 mg daily as needed. 1

Initial Dosing

• For hypertension, start with metoprolol tartrate 25-50 mg twice daily or metoprolol succinate (extended-release) 50-200 mg once daily 1
• For patients with concerns about beta-blocker tolerance (e.g., mild reactive airway disease), start with a lower dose of 12.5 mg of metoprolol 2
• In patients with atrial fibrillation, dosing should target a resting heart rate of 50-60 beats per minute unless limiting side effects occur 2, 1

Titration Protocol

• Increase dosage gradually every 1-2 weeks if blood pressure control or adequate heart rate control is not achieved 1
• Maximum recommended daily dose is 200 mg for metoprolol tartrate and 400 mg for metoprolol succinate 1
• For paroxysmal atrial fibrillation, titrate to achieve heart rate control while monitoring for side effects 1

Special Considerations

Intravenous Administration (for acute settings)

• Intravenous metoprolol may be given in 5-mg increments by slow intravenous administration (5 mg over 1-2 min), repeated every 5 min for a total initial dose of 15 mg 2, 1, 3
• After IV administration, oral therapy can be initiated 15 min after the last intravenous dose at 25 to 50 mg every 6 hours for 48 hours 2, 3
• Thereafter, patients should receive a maintenance dose of up to 100 mg twice daily 2, 3

High-Risk Patients

• For patients with mild wheezing or history of chronic obstructive pulmonary disease, use a reduced dose (e.g., 12.5 mg of metoprolol) rather than completely avoiding beta-blockers 2
• For patients at high risk of cardiogenic shock or with contraindications, starting at the lowest possible dose is particularly important 1
• Risk factors for cardiogenic shock include age >70 years, systolic BP <120 mm Hg, sinus tachycardia >110 bpm or heart rate <60 bpm 1, 4

Contraindications

• Absolute contraindications include signs of heart failure, low output state, increased risk for cardiogenic shock, PR interval >0.24 seconds, second or third-degree heart block, and active asthma or reactive airways disease 1
• Patients with marked first-degree AV block, any form of second- or third-degree AV block without a functioning pacemaker, history of asthma, severe LV dysfunction, or at high risk for shock should not receive beta blockers on an acute basis 2
• Patients with hypotension (systolic blood pressure <90 mm Hg), significant sinus bradycardia (heart rate <50 bpm), or evidence of a low-output state should not receive acute beta-blocker therapy until these conditions have resolved 2

Monitoring

• Monitor blood pressure and heart rate at each visit, with a target resting heart rate of 50-60 beats per minute unless limiting side effects occur 1
• During intravenous beta-blocker therapy, perform frequent checks of heart rate and blood pressure, continuous ECG monitoring, and auscultation for rales and bronchospasm 2
• Watch for signs of worsening heart failure or bronchospasm, particularly during initiation and with IV administration 1

Efficacy Considerations

• In patients with chronic atrial fibrillation and heart failure, aggressive heart rate control can be challenging due to patient intolerance of increasing doses of β-blockade 5
• For patients with stable angina and elevated heart rate despite low-dose beta-blocker therapy, higher doses of metoprolol succinate (190 mg) provide better heart rate control than lower doses (95 mg) 6
• Metoprolol CR/XL has been shown to effectively decrease mortality and improve clinical status in patients with chronic heart failure 7, 8