What is the recommended protocol for switching Lopressor (metoprolol) from oral to intravenous (IV) form?

Switching Lopressor (Metoprolol) from Oral to IV Form

When switching from oral to IV metoprolol, administer three bolus injections of 5 mg IV metoprolol at approximately 2-minute intervals, with continuous monitoring of blood pressure, heart rate, and ECG during administration. 1

Dosing Protocol for Oral to IV Conversion

• For patients previously on oral metoprolol who require IV administration, the recommended protocol is three bolus injections of 5 mg IV metoprolol given at approximately 2-minute intervals 1
• During IV administration, continuous monitoring of blood pressure, heart rate, and electrocardiogram is essential 1
• The maximum recommended IV dose is 15 mg total (three 5 mg boluses) 2, 1
• IV metoprolol should be administered in a setting with intensive monitoring capabilities 1

Returning to Oral Therapy

• After IV administration, patients who tolerated the full IV dose (15 mg) should receive metoprolol tartrate tablets 50 mg every 6 hours, starting 15 minutes after the last IV dose 1
• Continue this oral regimen for 48 hours, then transition to the maintenance dose of 100 mg orally twice daily 1
• For patients who did not tolerate the full IV dose, start with either 25 mg or 50 mg oral metoprolol every 6 hours (depending on the degree of intolerance) 15 minutes after the last IV dose 1
• In patients with severe intolerance, discontinuation of metoprolol may be necessary 1

Special Considerations

• Metoprolol IV administration is contraindicated in patients with:

  • Signs of heart failure 3
  • Low output state 3
  • Increased risk for cardiogenic shock 3
  • PR interval >0.24 seconds 3
  • Second or third-degree heart block 3
  • Active asthma or reactive airways disease 3

• Risk factors for cardiogenic shock include:

  • Age >70 years 2
  • Systolic blood pressure <120 mm Hg 2, 3
  • Sinus tachycardia >110 bpm or heart rate <60 bpm 2, 3
  • Increased time since onset of symptoms 2, 3

Monitoring Parameters

• Blood pressure and heart rate should be monitored continuously during IV administration and frequently after transition to oral therapy 3, 1
• Target resting heart rate is 50-60 beats per minute unless limiting side effects occur 3
• Monitor for signs of worsening heart failure or bronchospasm, particularly during IV administration 3
• Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration 1

Pharmacokinetic Considerations

• IV metoprolol provides rapid onset of action (within minutes) compared to oral formulations 4
• The time to response with IV metoprolol is typically less than 10 minutes, compared to an average of 5.1 hours with oral formulations 5
• After IV administration, plasma levels of metoprolol rapidly stabilize at approximately 200 nmol/L, which is sufficient to induce significant beta-blockade 4

Cautions and Pitfalls

• Avoid IV metoprolol in patients with decompensated heart failure 2
• Do not administer IV metoprolol in patients with pre-excitation and atrial fibrillation 2
• In patients with hepatic impairment, metoprolol blood levels may increase substantially, requiring lower doses and more cautious titration 1
• Elderly patients may require lower initial doses due to decreased hepatic, renal, or cardiac function 1
• The COMMIT trial showed that early IV metoprolol in acute MI patients increased risk of cardiogenic shock, particularly in high-risk patients 2