IV Metoprolol Initial Dosing
The initial dose of IV metoprolol is 5 mg administered slowly over 1-2 minutes, which can be repeated every 5 minutes up to a maximum total dose of 15 mg (three 5-mg boluses). 1, 2
Standard Dosing Protocol
- Administer 5 mg IV over 1-2 minutes as the first dose 1, 2
- Repeat 5 mg doses every 5 minutes as needed, monitoring response between each dose 1, 2
- Maximum initial total dose is 15 mg (three separate 5-mg injections) 1, 2
The FDA label specifies that injections should be given at approximately 2-minute intervals, though guidelines recommend every 5 minutes to allow adequate time for monitoring response 2, 1.
Transition to Oral Therapy
- Begin oral metoprolol 15 minutes after the last IV dose in patients who tolerate the full 15 mg IV dose 1, 2
- Initial oral dosing: 50 mg every 6 hours for 48 hours (or 25 mg every 6 hours if patient shows intolerance to full IV dose) 1, 2
- Maintenance dosing: 100 mg twice daily after the initial 48-hour period 1, 2
Critical Monitoring Requirements
During IV administration, you must perform:
- Frequent blood pressure and heart rate checks between each 5-mg dose 1, 2
- Continuous ECG monitoring throughout administration 1, 2
- Auscultation for rales (pulmonary congestion) and bronchospasm 1
- Target resting heart rate of 50-60 beats per minute unless limiting side effects occur 1
Absolute Contraindications - Do Not Give IV Metoprolol If:
- Signs of heart failure, low output state, or increased risk for cardiogenic shock 3
- Systolic BP <100-120 mm Hg with symptoms 3
- Heart rate <60 bpm or >110 bpm 3
- PR interval >0.24 seconds, second or third-degree heart block 3
- Active asthma or reactive airways disease 3
- Decompensated heart failure 3
Common Pitfalls to Avoid
- Administering doses too rapidly causes excessive hypotension - always give over 1-2 minutes 1
- Failing to monitor vital signs between doses may miss early adverse effects 1
- Never abruptly discontinue after starting - this can cause rebound hypertension, severe angina exacerbation, MI, and ventricular arrhythmias with 50% mortality in one study 3
Clinical Context
This dosing regimen was established primarily for acute myocardial infarction and supraventricular tachyarrhythmias 2, 4. Research demonstrates that mean doses of 6.5-9.5 mg IV effectively control ventricular rate in supraventricular arrhythmias, with response typically occurring within 10 minutes 4, 5. The 15 mg maximum dose achieves plasma concentrations around 200 nmol/L, which provides significant beta-blockade 6.