Esmolol to Metoprolol IV Dose Equivalency
There is no established direct dose equivalency between esmolol and metoprolol IV because they have fundamentally different pharmacokinetic profiles that make direct conversion inappropriate. 1
Why Direct Conversion Is Not Appropriate
Esmolol has an ultra-short elimination half-life of approximately 9 minutes, with full recovery from beta-blockade occurring 18-30 minutes after stopping the infusion 2, 3
Metoprolol IV has a duration of action of 5-8 hours, making it approximately 20-40 times longer-acting than esmolol 1
Esmolol is administered as a continuous infusion (typically 50-300 mcg/kg/min) after a loading dose, allowing for minute-to-minute titration 1, 4
Metoprolol IV is given as discrete boluses of 5 mg over 1-2 minutes, repeated every 5 minutes up to a maximum of 15 mg total 1, 5, 6
Clinical Approach to Transitioning
If you need to transition from esmolol to metoprolol IV, the recommended approach is:
Start with metoprolol 2.5-5 mg IV bolus over 2 minutes while continuing the esmolol infusion 1, 5
Monitor heart rate and blood pressure response for 5-10 minutes before considering additional metoprolol doses 1, 5
Gradually reduce or discontinue esmolol only after confirming adequate response to metoprolol, as metoprolol's effects will persist for hours 1, 6
Additional metoprolol 5 mg boluses can be given every 5 minutes up to a maximum total dose of 15 mg if needed for rate or blood pressure control 1, 5, 6
Important Safety Considerations
The 100 mcg dose you mentioned is likely too small to be clinically relevant - esmolol loading doses are typically 500 mcg/kg (approximately 35,000-50,000 mcg for an average adult), and maintenance infusions are 50-300 mcg/kg/min 1, 4
Both agents share the same contraindications: second or third-degree AV block, decompensated heart failure, cardiogenic shock, severe bradycardia, and active asthma 1, 5, 4
Metoprolol's longer duration means adverse effects (particularly hypotension and bradycardia) cannot be rapidly reversed by simply stopping the drug, unlike esmolol 2, 3
Continuous cardiac monitoring is essential during both esmolol infusion and metoprolol IV administration 5, 4