Metoprolol Succinate to IV Metoprolol Conversion
When converting from oral metoprolol succinate to IV metoprolol, use a ratio of approximately 1:1 where 100 mg of oral metoprolol succinate is equivalent to 5-10 mg of IV metoprolol given in divided doses. 1
Conversion Guidelines
The conversion from oral metoprolol succinate to IV metoprolol should follow these principles:
- Oral metoprolol succinate 50-100 mg daily ≈ IV metoprolol 5-10 mg (given as 2.5-5 mg IV boluses over 2 minutes, up to 3 doses) 1
- A 100 mg metoprolol controlled/extended-release tablet contains 95 mg of metoprolol succinate and is considered to have equivalent activity to 100 mg metoprolol tartrate 2
Dosing Protocol for IV Metoprolol
- Initial dose: 2.5-5 mg IV bolus over 2 minutes 1
- Repeat dosing: May repeat up to 3 doses at 2-5 minute intervals if needed 1
- Maximum IV dose: Generally 15 mg total in acute setting 1
- Continuous infusion: Not typically recommended for metoprolol (unlike esmolol)
Clinical Considerations
Hemodynamic Monitoring
- Monitor blood pressure and heart rate closely during conversion
- IV metoprolol has a more rapid onset of action (within minutes) compared to oral formulations
- Risk of hypotension is higher with IV administration, especially in patients with compromised cardiac function
Specific Clinical Scenarios
- Atrial fibrillation rate control: IV metoprolol 2.5-5 mg boluses are effective for acute rate control 1, 3
- Perioperative setting: IV metoprolol 2-4 mg has been used effectively during surgery 1
- Acute coronary syndromes: Start with lower doses (2.5 mg) in hemodynamically vulnerable patients
Pharmacokinetic Differences
- IV metoprolol: Immediate bioavailability (100%), rapid onset (1-2 minutes), shorter half-life (3-4 hours) 4
- Metoprolol succinate: Extended-release formulation designed for 20-24 hour duration, with relatively constant plasma concentrations 5
Common Pitfalls to Avoid
- Dosing error: Do not convert 1:1 mg-for-mg between oral and IV formulations
- Rapid administration: IV metoprolol should be given slowly (over 2 minutes per dose) to avoid precipitous drops in blood pressure
- Monitoring failure: Always monitor vital signs during and after IV administration
- Failure to adjust for patient factors: Reduce doses in hepatic impairment, as metoprolol is primarily metabolized by the liver 4
When transitioning back to oral therapy, the typical conversion is:
- IV metoprolol 5 mg ≈ oral metoprolol succinate 50-100 mg daily or metoprolol tartrate 25-50 mg twice daily 1