From the Guidelines
The equivalent IV dose of 25mg oral metoprolol is approximately 2.5mg IV, based on a 10:1 oral to IV conversion ratio due to significant first-pass metabolism and lower bioavailability of oral metoprolol 1. When converting from oral to intravenous metoprolol, it is essential to consider the pharmacokinetics of the drug. Metoprolol has significant first-pass metabolism when taken orally, resulting in lower bioavailability (about 50%) compared to IV administration 1. Therefore, the IV dose is typically one-tenth of the oral dose to achieve similar therapeutic effects.
- The recommended initial IV dose of metoprolol is 5 mg, given slowly over 1 to 2 minutes, and can be repeated every 5 minutes for a total initial dose of 15 mg 1.
- When administering IV metoprolol, it should be given slowly over 1-2 minutes to minimize the risk of hypotension and bradycardia.
- Vital signs should be monitored closely during administration, including frequent checks of heart rate and blood pressure, as well as continuous ECG monitoring 1.
- IV metoprolol has a faster onset of action compared to oral administration, typically within minutes rather than hours, which is important to consider when timing doses or monitoring for therapeutic effects. This conversion is particularly relevant in situations where a patient cannot take oral medications but requires continued beta-blocker therapy, such as in the management of unstable angina or non-ST-elevation myocardial infarction 1.
From the Research
Conversion of Oral Metoprolol to IV Amount
- The conversion of 25mg oral metoprolol to an IV amount is not directly stated in the provided studies 2, 3, 4, 5, 6.
- However, study 3 mentions that after IV administration of 20mg, patients with renal impairment showed an increase in clearance, whereas a decrease in clearance was seen in patients with hepatic cirrhosis.
- Study 6 reports the usage of high-dose intravenous metoprolol for heart rate reduction in CT coronary angiography, with an average usage of 19mg and a maximum dose of 67mg.
- It is essential to note that the conversion of oral to IV metoprolol may vary depending on individual patient factors, such as renal and hepatic function, and should be determined by a healthcare professional.
Pharmacokinetics of Metoprolol
- Study 3 provides a systematic review of the clinical pharmacokinetics of metoprolol, including its absorption, distribution, metabolism, and excretion.
- The study reports that metoprolol exhibits a dose-dependent increase in maximum plasma concentration, time to reach maximum plasma concentration, and area under the concentration-time curve after oral administration.
- The pharmacokinetics of metoprolol can be affected by various factors, including hepatic and renal function, as well as drug interactions 3.
Clinical Use of Metoprolol
- Metoprolol is commonly used for the treatment of hypertension, angina pectoris, and other cardiovascular conditions 2, 4, 5.
- Study 4 reports that oral metoprolol did not result in a significant drop in blood pressure compared to no treatment in patients with severe inpatient hypertension.
- Study 5 compares the effectiveness and safety of metoprolol and diltiazem for rate control of atrial fibrillation in the emergency department, with no significant difference in acute rate control effectiveness between the two groups.