How to titrate metoprolol (Lopressor) every 6 hours?

Metoprolol Every 6 Hours Titration Protocol

For acute myocardial infarction patients who tolerate IV metoprolol, start oral metoprolol tartrate 50 mg every 6 hours beginning 15 minutes after the last IV dose and continue for 48 hours, then transition to 100 mg twice daily for maintenance. 1

Standard IV to Oral Conversion Protocol

Initial IV Phase

• Administer three 5 mg IV boluses of metoprolol over 1-2 minutes each, separated by approximately 2-minute intervals, for a maximum total dose of 15 mg 1
• Monitor blood pressure, heart rate, and ECG continuously during IV administration 1

Transition to Every 6 Hour Dosing

• For patients tolerating full IV dose (15 mg): Start metoprolol tartrate 50 mg orally every 6 hours, beginning 15 minutes after the last IV dose 1
• Continue this every 6 hour regimen for 48 hours 1
• For patients with partial intolerance: Start 25 mg every 6 hours instead, depending on degree of intolerance 1

Transition to Maintenance Dosing

• After 48 hours of every 6 hour dosing, transition to 100 mg orally twice daily for long-term maintenance 1
• This represents the standard post-MI maintenance regimen 1

Critical Pre-Administration Contraindications

Absolute contraindications before giving metoprolol every 6 hours: 2

• Signs of heart failure, low output state, or decompensated heart failure
• Systolic BP <120 mm Hg
• Heart rate >110 bpm or <60 bpm
• PR interval >0.24 seconds or any second/third-degree heart block
• Active asthma or reactive airways disease

Monitoring During Every 6 Hour Dosing

• Check blood pressure and heart rate before each dose during the 48-hour every 6 hour period 2
• Monitor for signs of worsening heart failure including rales, increased dyspnea, or peripheral edema 2
• Watch for symptomatic bradycardia (HR <60 bpm with dizziness) or symptomatic hypotension (SBP <100 mmHg with symptoms) 2

Dose Adjustments During Titration

If adverse effects develop during every 6 hour dosing:

• For symptomatic bradycardia: Reduce dose by 50% (from 50 mg to 25 mg every 6 hours) 2
• For symptomatic hypotension: Hold dose if SBP <100 mmHg with symptoms 2
• For severe intolerance: Discontinue metoprolol entirely 1

Common Pitfalls to Avoid

• Never skip the every 6 hour phase in acute MI patients—this 48-hour period is part of the FDA-approved early treatment protocol 1
• Never use metoprolol succinate (extended-release) for the every 6 hour regimen—only metoprolol tartrate (immediate-release) should be dosed every 6 hours 2
• Never abruptly discontinue after starting—this can cause rebound ischemia, MI, and ventricular arrhythmias with 50% mortality in some studies 2
• Never give IV metoprolol to high-risk patients (age >70, SBP <120, HR >110 or <60, Killip class >1) as this increases cardiogenic shock risk by 11 per 1000 patients 2

Special Populations

• Elderly patients: Start at lower doses (25 mg every 6 hours) with cautious gradual titration given greater frequency of hepatic, renal, or cardiac dysfunction 1
• Hepatic impairment: Initiate at low doses (25 mg every 6 hours) with cautious gradual titration as blood levels increase substantially 1
• Renal impairment: No dose adjustment required 1