Lopressor mechanism of action
Clinical data | |
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Trade names | Lopressor, Toprol-xl |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682864 |
[[Regulation of therapeutic goods |Template:Engvar data]] |
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Routes of administration | Oral, IV |
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Pharmacokinetic data | |
Bioavailability | 12% |
Metabolism | Hepatic via CYP2D6, CYP3A4 |
Elimination half-life | 3-7 hours |
Excretion | Renal |
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E number | {{#property:P628}} |
ECHA InfoCard | {{#property:P2566}}Lua error in Module:EditAtWikidata at line 36: attempt to index field 'wikibase' (a nil value). |
Chemical and physical data | |
Formula | C15H25NO3 |
Molar mass | 267.364 g/mol |
3D model (JSmol) | |
Melting point | 120 °C (248 °F) |
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Mechanism of Action
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.
Clinical pharmacology studies have demonstrated the beta-blocking activity of metoprolol, as shown by:
- Reduction in heart rate and cardiac output at rest and upon exercise
- Reduction of systolic blood pressure upon exercise
- Inhibition of isoproterenol-induced tachycardia
- Reduction of reflex orthostatic tachycardia
Hypertension
The mechanism of the antihypertensive effects of beta-blocking agents has not been fully elucidated. However, several possible mechanisms have been proposed:
- Competitive antagonism of catecholamines at peripheral (especially cardiac) adrenergic neuron sites, leading to decreased cardiac output.
- A central effect leading to reduced sympathetic outflow to the periphery.
- 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, 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.
Myocardial Infarction
The precise mechanism of action of Lopressor in patients with suspected or definite myocardial infarction is not known.
References
Adapted from the FDA Package Insert.
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- Antianginals
- Antiarrhythmic agents
- Antihypertensive agents
- Antimigraine drugs
- Beta blockers
- Cardiovascular Drugs