Metoprolol Succinate (4 brand names, 2 dosage forms, 1 route)
Available dosage forms: CAPSULE, EXTENDED RELEASE, TABLET, EXTENDED RELEASE.
Routes of administration: ORAL.
Brand Names
- DUTOPROL
- KAPSPARGO SPRINKLE
- METOPROLOL SUCCINATE
- TOPROL-XL
Contraindications
Metoprolol succinate extended-release tablets are contraindicated in severe bradycardia, second- or third-degree heart block, cardiogenic shock, decompensated heart failure, sick sinus syndrome (unless a permanent pacemaker is in place), and in patients who are hypersensitive to any component of this product.
Adverse Reactions
The following adverse reactions are described elsewhere in labeling: Worsening angina or myocardial infarction [see Warnings and Precautions (5)]. Worsening heart failure [see Warnings and Precautions (5)]. Worsening AV block [see Contraindications (4)].
Mechanism of Action
Metoprolol is a beta 1-selective (cardioselective) adrenergic receptor blocking agent. This preferential effect is not absolute, however, and at higher plasma concentrations, metoprolol also inhibits beta 2-adrenoreceptors, chiefly located in the bronchial and vascular musculature. Metoprolol has no intrinsic sympathomimetic activity, and membrane-stabilizing activity is detectable only at plasma concentrations much greater than required for beta-blockade. Animal and human experiments indicate that metoprolol slows the sinus rate and decreases AV nodal conduction. The relative beta 1-selectivity of metoprolol has been confirmed by the following: (1) In normal subjects, metoprolol is unable to reverse the beta 2-mediated vasodilating effects of epinephrine. This contrasts with the effect of nonselective beta-blockers, which completely reverse the vasodilating effects of epinephrine. (2) In asthmatic patients, metoprolol reduces FEV 1and FVC significantly less than a nonselective beta-blocker, propranolol, at equivalent beta 1-receptor blocking doses. Hypertension:The mechanism of the antihypertensive effects of beta-blocking agents has not been elucidated. However, several possible mechanisms have been proposed: (1) competitive antagonism of catecholamines at peripheral (especially cardiac) adrenergic neuron sites, leading to decreased cardiac output; (2) a central effect leading to reduced sympathetic outflow to the periphery; and (3) suppression of renin activity. Angina Pectoris: By blocking catecholamine-induced increases in heart rate, in velocity and extent of myocardial contraction, and in blood pressure, metoprolol reduces the oxygen requirements of the heart at any given level of effort, thus making it useful in the long-term management of angina pectoris. Heart Failure:The precise mechanism for the beneficial effects of beta-blockers in heart failure has not been elucidated.
Overdosage
Signs and Symptoms - Overdosage of metoprolol succinate extended-release tablets may lead to severe bradycardia, hypotension, and cardiogenic shock. Clinical presentation can also include atrioventricular block, heart failure, bronchospasm, hypoxia, impairment of consciousness/coma, nausea and vomiting. Treatment – Consider treating the patient with intensive care. Patients with myocardial infarction or heart failure may be prone to significant hemodynamic instability. Beta-blocker overdose may result in significant resistance to resuscitation with adrenergic agents, including beta-agonists. On the basis of the pharmacologic actions of metoprolol, employ the following measures: Hemodialysis is unlikely to make a useful contribution to metoprolol elimination [see Clinical Pharmacology (12.3)] . Bradycardia: Evaluate the need for atropine, adrenergic-stimulating drugs, or pacemaker to treat bradycardia and conduction disorders. Hypotension: Treat underlying bradycardia. Consider intravenous vasopressor infusion, such as dopamine or norepinephrine. Heart failure and shock: May be treated when appropriate with suitable volume expansion, injection of glucagon (if necessary, followed by an intravenous infusion of glucagon), intravenous administration of adrenergic drugs such as dobutamine, with α 1receptor agonistic drugs added in presence of vasodilation. Bronchospasm: Can usually be reversed by bronchodilators.