Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2018 Publisher: Recordati Ireland Ltd., Raheens East, Ringaskiddy, Co. Cork, Ireland
Pharmacotherapeutic group: Beta blocking agents, selective
ATC code: C07AB02
Metoprolol is a competitive beta-adrenoceptor antagonist. It acts preferentially to inhibit beta-adrenoceptors (conferring some cardioselectivity), is devoid of intrinsic sympathomimetic activity (partial agonist activity) and possesses beta-adrenoceptor blocking activity comparable in potency with propranolol.
A negative chronotrophic effect on the heart is a consistent feature of metoprolol administration. Thus, cardiac output and systolic blood pressure rapidly decrease following acute administration.
The intention to treat trial COMMIT included 45,852 patients admitted to hospital within 24 hours of the onset of symptoms of suspected acute myocardial infarction with supporting ECG abnormalities (i.e. ST elevation, ST depression or left bundle-branch block). Patients were randomly allocated to metoprolol (up to 15 mg intravenous then 200 mg oral) or placebo and treated until discharge or up to 4 weeks in hospital. The two co-primary outcomes were: (1) composite of death, reinfarction or cardiac arrest; and (2) death from any cause during the scheduled treatment period. Neither of the co-primary outcomes was significantly reduced by metoprolol. However, metoprolol treatment was associated with fewer people having reinfarction and ventricular fibrillation but an increased rate of cardiogenic shock during the first day after admission. There was substantial net hazard in haemodynamically unstable patients. There was moderate net benefit in those who were stable, particularly after days 0-1.
Metoprolol undergoes oxidative metabolism in the liver primarily by the CYP2D6 isoenzyme.
Metoprolol is eliminated mainly by hepatic metabolism, the average elimination half-life is 3.5 hours (range 1-9 hours). Rates of metabolism vary between individuals, with poor metabolisers (approximately 10%) showing higher plasma concentrations and slower elimination than extensive metabolisers. Within individuals, however, plasma concentrations are stable and reproducible.
Pre-clinical information has not been included because the safety profile of metoprolol tartrate has been established after many years of clinical use. Please refer to section 4.
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