What are the dosing parameters for PRN (as needed) intravenous (IV) metoprolol for tachycardia?

From the Guidelines

For PRN IV metoprolol to treat tachycardia, the typical parameters include administering 2.5–5 mg bolus over 2 min, which can be repeated as needed, with a maximum dose not explicitly stated in the most recent guidelines 1.

Key Considerations

• The most recent guidelines from 2023 do not specify a maximum number of doses or a total maximum dose for IV metoprolol in the context of tachycardia management 1.
• However, previous guidelines suggest that metoprolol can be given in 5-mg increments by slow intravenous administration (5 mg over 1 to 2 min), repeated every 5 min for a total initial dose of 15 mg 1.
• It is crucial to monitor the patient's heart rate, blood pressure, and cardiac rhythm continuously during and after administration.
• Metoprolol works by blocking beta-1 adrenergic receptors in the heart, reducing sympathetic stimulation which slows heart rate and decreases cardiac contractility.

Important Precautions

• This medication should be used cautiously in patients with bronchospastic disease, diabetes, or heart failure.
• It is contraindicated in severe bradycardia, heart block, cardiogenic shock, or decompensated heart failure.

Administration and Monitoring

• Before administration, check baseline vital signs and obtain a 12-lead ECG if possible.
• Hold the medication if heart rate drops below 60 beats per minute, if systolic blood pressure falls below 100 mmHg, or if the patient develops signs of heart failure or heart block.
• The choice of beta blocker for an individual patient is based primarily on pharmacokinetic and side effect criteria, as well as on physician familiarity 1.

From the FDA Drug Label

DOSAGE & ADMINISTRATION Myocardial Infarction Early Treatment During the early phase of definite or suspected acute myocardial infarction, initiate treatment with metoprolol tartrate as soon as possible after the patient’s arrival in the hospital. Such treatment should be initiated in a coronary care or similar unit immediately after the patient’s hemodynamic condition has stabilized Begin treatment in this early phase with the intravenous administration of three bolus injections of 5 mg of metoprolol tartrate injection each; give the injections at approximately 2-minute intervals.

The dosing parameters for PRN (as needed) intravenous (IV) metoprolol for tachycardia are not explicitly stated in the provided drug label. The label only provides dosing information for the treatment of myocardial infarction, not for tachycardia. Therefore, no conclusion can be drawn regarding the dosing parameters for PRN IV metoprolol for tachycardia 2.

From the Research

Dosing Parameters for PRN IV Metoprolol for Tachycardia

• The dosing parameters for PRN (as needed) intravenous (IV) metoprolol for tachycardia are not explicitly stated in the provided studies as a specific protocol for PRN administration.
• However, the studies provide information on the dosing of IV metoprolol for tachycardia:
  • A study from 1991 3 used a mean dose of 9.5 mg (range: 2-15 mg) administered in one or two separate infusions of up to 7.5 mg each over a cumulative maximum interval of 25 minutes.
  • Another study from 2021 4 compared the effectiveness of IV metoprolol and diltiazem for rate control of supraventricular tachycardia, but does not specify the dosing regimen for PRN administration.
  • A study from 2022 5 evaluated the effectiveness and safety of IV metoprolol versus diltiazem for atrial fibrillation with concomitant heart failure, but also does not provide specific dosing parameters for PRN administration.

Administration and Efficacy

• IV metoprolol has been shown to be effective in controlling ventricular rate in patients with supraventricular tachyarrhythmias 3, 4, 5.
• The efficacy of IV metoprolol in achieving rate control is similar to that of diltiazem in some studies 4, 5, but may have a slower onset of action 5.
• IV metoprolol has been used in various dosing regimens, including bolus doses and continuous infusions, but the optimal dosing strategy for PRN administration is not well established.

Safety Considerations

• Hypotension is a potential side effect of IV metoprolol, particularly when used in combination with other medications or in patients with certain medical conditions 3, 4, 6, 5.
• Bradycardia is another potential side effect of IV metoprolol, although it is less common than hypotension 4, 5.
• The safety profile of IV metoprolol is generally favorable, but patients should be closely monitored for potential side effects, particularly when used in a PRN administration protocol.