What is the dosing frequency for intravenous (IV) metoprolol (beta-blocker) administration?

IV Metoprolol Dosing Frequency

IV metoprolol should be administered in 5-mg increments by slow intravenous administration (5 mg over 1 to 2 minutes), repeated every 5 minutes for a total initial dose of 15 mg. 1

Dosing Protocol for IV Metoprolol

• Initial IV dosing: 5 mg increments given slowly over 1-2 minutes 1
• Frequency: Repeat doses every 5 minutes 1
• Maximum initial IV dose: Total of 15 mg (three 5-mg doses) 1
• Transition to oral therapy: In patients who tolerate the total 15-mg IV dose, oral therapy can be initiated 15 minutes after the last intravenous dose 1
• Initial oral dosing after IV administration: 25 to 50 mg every 6 hours for 48 hours 1
• Maintenance oral dosing: Up to 100 mg twice daily 1

Monitoring During IV Beta-Blocker Therapy

• Frequent checks of heart rate and blood pressure 1
• Continuous ECG monitoring 1
• Auscultation for rales and bronchospasm 1
• Target resting heart rate: 50-60 beats per minute unless a limiting side effect is reached 1

Contraindications and Precautions

• Do not administer to patients with:

  • Low-output state (e.g., oliguria) 1
  • Significant sinus bradycardia (heart rate less than 50 beats per minute) 1
  • Hypotension (systolic blood pressure less than 90 mm Hg) 1
  • Severe left ventricular dysfunction or heart failure 1
  • High risk for cardiogenic shock 1

• Use with caution in patients with:

  • Chronic obstructive pulmonary disease with reactive airway component 1
  • History of asthma (consider reduced doses) 1
  • Mild wheezing (use reduced doses of cardioselective agents) 1

Clinical Pearls

• IV metoprolol is a beta-1 selective blocker that can be administered safely when appropriate monitoring is in place 1
• Plasma levels of metoprolol stabilize at approximately 200 nmol/L after the initial IV and oral dosing regimen 2
• There is a significant correlation between change in resting heart rate and plasma concentration of metoprolol 15 minutes after starting treatment 2, 3
• The effect on heart rate is linearly related to the logarithm of the plasma concentration 3
• Metoprolol's beta-1 selectivity may be lost at higher plasma concentrations, so adhering to recommended dosing is important 4

Common Pitfalls to Avoid

• Administering IV metoprolol too rapidly (faster than 1-2 minutes per 5 mg dose) can lead to excessive hypotension 1
• Failing to monitor vital signs between doses may result in missing early signs of adverse effects 1
• Not allowing sufficient time between doses (minimum 5 minutes) can lead to drug accumulation and excessive beta-blockade 1
• Overlooking contraindications, particularly signs of heart failure or hypotension 1
• Abrupt discontinuation of beta-blockers should be avoided to prevent rebound hypertension or tachycardia 5