Metoprolol is a beta-Adrenergic blocking agent. Beta receptors are part of the sympathetic nervous system and are found on cells of the heart, smooth muscles, in airways, arteries and kidneys. Associated with stress response, they are stimulated by epinephrine. Beta blockers interfere with the binding of epinephrine at the receptors. Metoprolol works by inhibiting the response to adrenergic stimuli by blocking beta one adrenergic receptors within the myocardium. (Hoffman, Jones Reeder, & Rodgers, 2000) Conduction is slowed through the SA and AV nodes. A decrease in the resting heart rate and negative inotropic effects are seen; thus decreasing the cardiac output at rest and during exercise. Reduction of blood pressure is achieved by decreasing the cardiac output, decreasing sympathetic outflow from the CNS, as well as suppressing renin release which reduces peripheral vascular resistance. (www.drugs.com) The primary indication for Metoprolol is in post myocardial infarction and management of angina. Early administration of Metoprolol within hours of AMI has been shown to reduce mortality in these patients. (Hoffman et al., 2000) Other indications include treatment of hypertension. It is one of the preferred initial therapies in hypertensive patients with ischemic heart disease and heart failure. Metoprolol has also been successful in treatment of some supraventricular tachyarrhythmias including paroxysmal SVT, reentry SVT, multifocal atrial tachycardia, and junctional tachycardia. It can also be considered for rate control in atrial fibrillation/atrial flutter in patients with preserved left ventricular function. (www.drugs.com) When used in conjunction with ACE inhibitors, diuretics, and cardiac glycosides it can be used to treat New York Heart Association class II and class III heart failure. (www.drugs.com) Metoprolol is available for both oral and intravenous administration. The oral tablets are available in both extended...
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