From the Guidelines
Metoprolol XL (extended-release) has a duration of action of approximately 24 hours, which allows for once-daily dosing. This extended-release formulation maintains therapeutic blood levels throughout the day by slowly releasing the medication from a matrix system in the gastrointestinal tract. The active ingredient, metoprolol, is a selective beta-1 adrenergic receptor blocker that reduces heart rate and blood pressure by blocking the effects of adrenaline on the heart.
Key Points to Consider
- Patients should take metoprolol XL at the same time each day to maintain consistent blood levels, and the tablet should be swallowed whole, not crushed or chewed, as this would destroy the extended-release mechanism and potentially cause too much medication to be released at once.
- If a dose is missed, patients should take it as soon as remembered unless it's almost time for the next dose, in which case they should skip the missed dose and continue with their regular schedule.
- Abrupt discontinuation should be avoided as it can worsen underlying conditions; dosage should be gradually reduced over 1-2 weeks under medical supervision.
Evidence Supporting the Recommendation
The most recent and highest quality study, 1, provides information on the pharmacological agents for rate control in patients with atrial fibrillation, including metoprolol succinate, which has an elimination half-life of 3-7 hours, supporting the once-daily dosing of metoprolol XL.
Administration and Dosage
- The oral maintenance dose of metoprolol succinate is 50-400 mg daily or twice daily in 3-7 divided doses.
- It is essential to individualize the dose and titrate to the desired effect, considering the patient's response and potential side effects.
From the Research
Duration of Action of Metoprolol XL
The duration of action of metoprolol XL (extended-release) can be understood through its pharmacokinetic and pharmacodynamic properties.
- Metoprolol is a beta1-selective adrenoceptor blocking drug, and its duration of effect is longer than expected from its half-life, making it suitable for twice daily administration or even once daily administration in treating hypertension 2.
- Controlled release metoprolol formulations, such as metoprolol CR/ZOK and metoprolol OROS, release the drug at a relatively constant rate over a 24-hour period, producing sustained and consistent metoprolol plasma concentrations and beta 1-blockade while retaining the convenience of once daily administration 3.
- The Metoprolol CR/XL Randomized Intervention Trial in Congestive Heart Failure (MERIT-HF) demonstrated that metoprolol CR/XL can be safely titrated in patients with stable mild to moderate heart failure, with minimal side effects or deterioration, and its effects on mortality and morbidity can be determined over a long period 4, 5.
- A study comparing the pharmacokinetics and pharmacodynamics of immediate-release metoprolol with controlled-release/extended-release metoprolol (CR/XL) found that metoprolol CR/XL 200 mg once daily was associated with a more pronounced suppression of heart rate than metoprolol IR 50 mg, suggesting that patients can safely be switched from multiple dosing of metoprolol IR to a once-daily dose of metoprolol CR/XL 6.
Key Findings
- Metoprolol XL has a duration of action that allows for once daily administration.
- Controlled release formulations of metoprolol provide consistent plasma concentrations over 24 hours.
- Metoprolol CR/XL is safe and effective in patients with heart failure, with minimal side effects or deterioration.
- The pharmacokinetics and pharmacodynamics of metoprolol CR/XL support its use as a once daily medication.