Lopressor mechanism of action

Metoprolol

Clinical data
Trade names	Lopressor, Toprol-xl
AHFS/Drugs.com	Monograph
MedlinePlus	a682864
[[Regulation of therapeutic goods |Template:Engvar data]]	US FDA: Metoprolol
Pregnancy category	AU: C US: C (Risk not ruled out)
Routes of administration	Oral, IV
ATC code	C07AB02 (WHO)
Legal status
Legal status	In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability	12%
Metabolism	Hepatic via CYP2D6, CYP3A4
Elimination half-life	3-7 hours
Excretion	Renal
Identifiers
IUPAC name (RS)-1-(Isopropylamino)-3-[4-(2-methoxyethyl)phenoxy]propan-2-ol
CAS Number	51384-51-1 Y
PubChem CID	4171
IUPHAR/BPS	553
DrugBank	DB00264 Y
ChemSpider	4027 Y
UNII	GEB06NHM23
KEGG	D02358 Y
ChEBI	CHEBI:6904 Y
ChEMBL	ChEMBL13 Y
E number	{{#property:P628}}
ECHA InfoCard	{{#property:P2566}}
Chemical and physical data
Formula	C15H25NO3
Molar mass	267.364 g/mol
3D model (JSmol)	Interactive image
Melting point	120 °C (248 °F)
SMILES O(c1ccc(cc1)CCOC)CC(O)CNC(C)C
InChI InChI=1S/C15H25NO3/c1-12(2)16-10-14(17)11-19-15-6-4-13(5-7-15)8-9-18-3/h4-7,12,14,16-17H,8-11H2,1-3H3 Y Key:IUBSYMUCCVWXPE-UHFFFAOYSA-N Y
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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.