From the Guidelines
To convert metoprolol extended-release (ER) 25 mg oral dose to an intravenous (IV) dose, use a 1:2 ratio, which means 12.5 mg IV metoprolol would be equivalent to 25 mg oral ER metoprolol, as suggested by the guidelines 1. When switching from oral to IV metoprolol, the IV dose should be administered as 5 mg slow IV boluses every 5 minutes, not exceeding a total of 15 mg, according to the recommendations 1. For the 25 mg ER oral dose, two 5 mg IV boluses (10 mg total) would be appropriate in most cases, considering the difference in bioavailability between oral and IV routes, as oral metoprolol undergoes significant first-pass metabolism in the liver, resulting in approximately 50% bioavailability 1. The IV form bypasses this first-pass effect, making it more potent at lower doses. When administering IV metoprolol, monitor the patient's heart rate and blood pressure closely during and after administration, as the IV route produces more immediate hemodynamic effects compared to the gradual release of the ER oral formulation, and be cautious of potential contraindications such as signs of heart failure, low output state, or increased risk of cardiogenic shock 1. Key considerations for metoprolol administration include:
- Starting with a low dose and titrating as needed
- Monitoring for signs of heart failure, hypotension, or bronchospasm
- Avoiding use in patients with contraindications such as heart failure, low output state, or increased risk of cardiogenic shock
- Using the 1:2 ratio for converting oral to IV doses, as supported by the guidelines 1.
From the FDA Drug Label
In patients who tolerate the full intravenous dose (15 mg), initiate metoprolol tartrate tablets, 50 mg every 6 hours, 15 minutes after the last intravenous dose and continued for 48 hours. Start patients who appear not to tolerate the full intravenous on metoprolol tartrate tablets either 25 mg or 50 mg every 6 hours (depending on the degree of intolerance) 15 minutes after the last intravenous dose or as soon as their clinical condition allows.
The conversion from Metoprolol 25mg ER po to IV is not directly stated in the label for the specific dose of 25mg ER. However, the label does provide information on initiating oral doses after IV administration.
- For patients who tolerate the full IV dose, the oral dose is 50 mg every 6 hours.
- For patients who do not tolerate the full IV dose, the oral dose can be 25 mg or 50 mg every 6 hours, depending on the degree of intolerance. Since the label does not provide a direct conversion for 25mg ER po to IV, and considering the information provided is for initiation of oral therapy after IV administration, no direct conversion can be determined from the provided label information 2.
From the Research
Metoprolol 25mg ER po to IV Conversion
- The provided studies do not directly address the conversion of metoprolol 25mg ER po to IV.
- However, it is known that metoprolol succinate is a controlled-release formulation, and its oral bioavailability is approximately 50% 3.
- When converting from oral to intravenous metoprolol, the dose is typically reduced due to the differences in bioavailability.
- A common conversion ratio is to use 1/4 to 1/2 of the oral dose when switching to intravenous administration, but this may vary depending on the specific clinical situation and patient factors.
- It is recommended to consult a reliable clinical resource or a pharmacist for guidance on converting metoprolol 25mg ER po to IV, as the exact conversion ratio may not be well-established in the provided studies 4, 3, 5, 6, 7.