What is the onset time of metoprolol (beta blocker)?

From the Guidelines

Metoprolol begins to work within 1 hour after oral administration, with peak effects occurring at approximately 2-4 hours, as noted in the guidelines for the management of patients with unstable angina/non-st-elevation myocardial infarction 1. When given intravenously, the onset of action is much faster, typically within minutes. The medication works by blocking beta-1 adrenergic receptors in the heart, which reduces heart rate, blood pressure, and cardiac workload.

Key Points:

• The onset of action for oral metoprolol is within 1 hour, with peak effects at 2-4 hours.
• Intravenous metoprolol has a much faster onset of action, typically within minutes.
• Metoprolol is recommended to be initiated orally, in the absence of contraindications, within the first 24 hours 1.
• 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.
• Patients should be aware that while some effects occur quickly, the maximum therapeutic benefit for conditions like hypertension or angina may require consistent dosing over several days to weeks.

Administration:

• Intravenous metoprolol may 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.
• In patients who tolerate the total 15-mg IV dose, oral therapy can be initiated 15 min after the last intravenous dose at 25 to 50 mg every 6 h for 48 h.
• Maintenance doses are given in Table 15, with a target resting heart rate of 50 to 60 beats per minute unless a limiting side effect is reached 1.

From the Research

Onset Time of Metoprolol

• The onset time of metoprolol is not explicitly stated in the provided studies, but the antihypertensive effect of metoprolol given at a dosage of 200 mg per day was more rapid in onset after the ordinary tablet formulation compared to the sustained-release formulation 2.
• A study comparing ordinary metoprolol tablets and metoprolol sustained-release tablets found that the antihypertensive effect of metoprolol was significant at 2 hours after administration of the ordinary tablet formulation, but not at 2 hours after administration of the sustained-release formulation 2.
• The pharmacokinetic properties of extended-release metoprolol succinate, a controlled-release formulation, produce even plasma concentrations over a 24-h period, without the marked peaks and troughs characteristically observed with the immediate-release formulation 3.
• The onset of action of metoprolol CR/XL, a controlled-release formulation, is not explicitly stated, but it has been shown to be effective in reducing mortality and improving clinical status in patients with stable mild to moderate chronic heart failure due to left ventricular systolic dysfunction 4.

Comparison of Formulations

• The ordinary tablet formulation of metoprolol has a more rapid onset of action compared to the sustained-release formulation 2.
• The controlled-release formulations of metoprolol, such as metoprolol CR/XL and metoprolol OROS, produce sustained beta 1-blockade over a 24-hour period and minimize the loss of selectivity associated with higher plasma concentrations 5, 6.
• Extended-release metoprolol succinate is a controlled-release formulation designed to deliver metoprolol succinate at a near constant rate for approximately 20 hours, independent of food intake and gastrointestinal pH 3.