How do I start metoprolol (beta-blocker) therapy?

Initiating Metoprolol Therapy

When starting metoprolol, begin with a low dose of 12.5-25 mg once daily for metoprolol succinate (extended-release) or 25 mg twice daily for metoprolol tartrate, then gradually titrate upward every 2 weeks to target or maximum tolerated dose. 1

Dosing Protocols by Formulation

Metoprolol Succinate (Extended-Release)

• Initial dose: 12.5-25 mg once daily
• Target dose: 200 mg once daily
• Titration: Increase dose at 2-week intervals
• Administration: Take once daily with or without food

Metoprolol Tartrate (Immediate-Release)

• Initial dose: 25 mg twice daily
• Target dose: 100 mg twice daily
• Titration: Increase dose every 2 weeks
• Administration: Take with or without food at consistent times

Clinical Context-Specific Protocols

For Post-Myocardial Infarction

1. Acute phase (if hemodynamically stable):

   • Begin with three 5 mg IV boluses at 2-minute intervals (total 15 mg)
   • Monitor blood pressure, heart rate, and ECG during administration
   • If tolerated, start oral metoprolol tartrate 50 mg every 6 hours, 15 minutes after last IV dose
   • Continue for 48 hours, then transition to 100 mg twice daily maintenance 2

2. If IV bolus not fully tolerated:

   • Start with 25-50 mg oral dose every 6 hours (based on degree of intolerance)
   • Discontinue if severe intolerance occurs 2

For Heart Failure

• Initial dose: 12.5-25 mg once daily of metoprolol succinate
• Target dose: 200 mg once daily
• Titration: Double dose every 2 weeks as tolerated
• Prerequisite: Patient should be on optimal doses of ACEIs/ARBs
• Monitoring: Watch for signs of worsening heart failure during uptitration 3, 1

For Hypertension or Angina

• Initial dose: 25-50 mg twice daily of metoprolol tartrate or 50-100 mg once daily of metoprolol succinate
• Target dose: Based on blood pressure or symptom control
• Maximum dose: 200 mg daily (succinate) or 400 mg daily (tartrate) 4, 5

Monitoring During Initiation and Titration

1. Before starting:

   • Check baseline heart rate (avoid if <50 bpm)
   • Check blood pressure (avoid if systolic BP <90 mmHg)
   • Assess for signs of heart failure or cardiogenic shock
   • Review for contraindications (asthma, severe heart block)

2. During titration:

   • Monitor heart rate and blood pressure at each dose increase
   • Assess for signs of worsening heart failure (weight gain, edema, dyspnea)
   • Check for symptomatic bradycardia or hypotension
   • Consider temporary dose reduction if side effects occur 3, 1

Precautions and Contraindications

Absolute Contraindications

• Severe bradycardia (heart rate <50 bpm)
• Second or third-degree heart block without pacemaker
• Cardiogenic shock
• Decompensated heart failure requiring IV inotropic therapy
• Severe asthma 3

Relative Contraindications (Use with Caution)

• Compensated heart failure (start at very low dose)
• COPD without bronchospasm
• Diabetes (may mask hypoglycemia symptoms)
• Peripheral vascular disease 3

Managing Common Issues During Initiation

Hypotension

• If symptomatic, consider reducing doses of other antihypertensives first
• If persistent, temporarily reduce metoprolol dose
• Do not discontinue abruptly 3

Bradycardia

• If heart rate <50 bpm but asymptomatic, monitor closely
• If symptomatic, reduce dose or temporarily discontinue
• Consider reducing doses of other medications affecting heart rate 3

Worsening Heart Failure

• Increase diuretic dose first
• Consider temporarily reducing metoprolol dose
• Do not discontinue abruptly unless severe decompensation 3

Important Caveats

• Never stop metoprolol abruptly due to risk of rebound hypertension, increased myocardial ischemia, and arrhythmias 1
• In patients with recent heart failure decompensation, initiate only after stabilization and preferably before discharge 3
• The "start low, go slow" approach is essential, particularly in heart failure patients 1
• Once-daily dosing with metoprolol succinate may improve adherence compared to twice-daily dosing with metoprolol tartrate 4, 5
• For patients at high risk of cardiogenic shock (age >70, systolic BP <120 mmHg, heart rate >110 bpm, or Killip class >1), use extreme caution when initiating therapy 3

By following these structured guidelines for metoprolol initiation and titration, you can maximize therapeutic benefits while minimizing adverse effects.