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| __NOTOC__
| | #REDIRECT [[Metoprolol tartrate#Pharmacology]] |
| {{Metoprolol}}
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| {{CMG}}
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| ===Mechanism of Action===
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| Lopressor is a [[beta1]]-selective (cardioselective) adrenergic receptor blocker. This preferential effect is not absolute, however, and at higher plasma concentrations, Lopressor also inhibits [[beta2]]-adrenoreceptors, chiefly located in the bronchial and vascular musculature.
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| Clinical pharmacology studies have demonstrated the beta-blocking activity of metoprolol, as shown by:
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| * Reduction in [[heart rate]] and [[cardiac output]] at rest and upon exercise
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| * Reduction of [[systolic blood pressure]] upon exercise
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| * Inhibition of [[isoproterenol]]-induced [[tachycardia]]
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| * Reduction of reflex [[orthostatic]] [[tachycardia]]
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| ====Hypertension====
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| The mechanism of the [[antihypertensive]] effects of beta-blocking agents has not been fully elucidated. However, several possible mechanisms have been proposed:
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| * Competitive antagonism of [[catecholamine]]s at peripheral (especially cardiac) adrenergic neuron sites, leading to decreased [[cardiac output]].
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| * A central effect leading to reduced [[sympathetic]] outflow to the periphery.
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| * Suppression of [[renin]] activity
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| ====Angina Pectoris====
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| By blocking [[catecholamine]]-induced increases in heart rate, in velocity and extent of myocardial contraction, and in [[blood pressure]], Lopressor 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]].
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| ====Myocardial Infarction====
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| The precise mechanism of action of Lopressor in patients with suspected or definite [[myocardial infarction]] is not known.
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| ==References==
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| {{Reflist}}
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| {{FDA}}
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| [[Category:Antianginals]]
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| [[Category:Antiarrhythmic agents]]
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| [[Category:Antihypertensive agents]]
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| [[Category:Antimigraine drugs]]
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| [[Category:Beta blockers]]
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| [[Category:Cardiovascular Drugs]]
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