What is the recommended dosage and administration of metoprolol (beta-blocker) intravenously (IV)?

IV Metoprolol Dosing and Administration

Administer metoprolol as 5 mg IV bolus over 2 minutes, repeated every 5 minutes up to a maximum total dose of 15 mg (three doses), with continuous monitoring of heart rate, blood pressure, and ECG throughout administration. 1, 2

Standard Dosing Protocol

• Initial dose: 2.5-5 mg IV bolus administered slowly over 1-2 minutes 1, 3, 2
• Repeat dosing: May repeat 5 mg every 5 minutes based on hemodynamic response 1, 3, 2
• Maximum total dose: 15 mg (three 5 mg boluses) 1, 3, 2
• Onset of action: 1-2 minutes 1
• Duration of action: 5-8 hours 1

Transition to Oral Therapy

• Timing: Begin oral metoprolol 15 minutes after the last IV dose in patients who tolerate the full 15 mg IV dose 3, 2
• Initial oral dosing: 25-50 mg every 6 hours for 48 hours (depending on tolerance) 3, 2
• Maintenance dosing: 100 mg orally twice daily thereafter 3, 2, 4

Absolute Contraindications

Do not administer IV metoprolol if any of the following are present:

• Signs of heart failure, low output state, or decompensated heart failure 1, 3
• Systolic blood pressure <120 mmHg 1
• Heart rate >110 bpm or <60 bpm 1
• Second or third-degree AV block (without pacemaker) 1, 3
• PR interval >0.24 seconds 1
• Active asthma or reactive airway disease 1, 3
• Cardiogenic shock or high risk factors (age >70 years, Killip class >1) 1, 3

Required Monitoring During Administration

Continuous monitoring is mandatory and includes:

• Heart rate monitoring continuously 3
• Blood pressure checks between each dose 3, 2
• Continuous ECG monitoring 3, 2
• Auscultation for new rales (pulmonary congestion) 3
• Auscultation for bronchospasm 3

Clinical Context and Indications

IV metoprolol is indicated for:

• Acute myocardial infarction (early treatment phase) 2, 4
• Supraventricular tachycardia unresponsive to adenosine or vagal maneuvers 5
• Atrial fibrillation/flutter with rapid ventricular response (rate control) 5
• Hypertensive emergencies with acute coronary syndrome 1

Critical Pitfalls to Avoid

• Never administer the full 15 mg as a single rapid bolus - this significantly increases risk of severe hypotension and bradycardia 5, 3
• Never give IV metoprolol in decompensated heart failure - this increases cardiogenic shock risk by 11 per 1000 patients treated 5
• Never use in pre-excited atrial fibrillation (WPW syndrome) - may paradoxically accelerate ventricular response 5
• Do not fail to monitor vital signs between doses - missing early signs of adverse effects can lead to serious complications 3
• Avoid abrupt discontinuation - can cause severe exacerbation of angina, myocardial infarction, and ventricular arrhythmias with 50% mortality in some studies 5

Special Populations

• Elderly patients (>65 years): Initiate at low doses with cautious gradual titration due to decreased hepatic, renal, or cardiac function 2
• Hepatic impairment: Blood levels increase substantially; initiate at low doses with cautious gradual titration 2
• Renal impairment: No dose adjustment required 2
• Women: May require 50% lower doses due to 50-80% higher drug exposure compared to men 5

Alternative for High-Risk Patients

For patients at high risk of adverse effects, consider esmolol instead of metoprolol:

• Loading dose: 500 mcg/kg over 1 minute 5
• Maintenance infusion: 50-300 mcg/kg/min 5, 3
• Advantage: Ultra-short half-life (10-30 minutes) allows rapid titration and reversal 1