Brands, Medical Use, Clinical Data
Drug Category
- Sympatholytics
- Antihypertensive Agents
- Antiarrhythmic Agents
- Adrenergic Agents
Dosage Forms
Brands / Synonyms
Beloc; Betaloc; Dutoprol; Lopresor; Lopresoretic; Lopressor; Lopressor HCT; Metoprolol; Metoprolol and Hydrochlorothiazide; Metoprolol Tartrate; Metroprolol; Prelis; Selo-Zok; Seloken; Selopral; Toprol; Toprol-XL; Toprol-XL
Indications
For the treatment of hypertension and angina pectoris.
Pharmacology
Metoprolol, a competitive, beta1-selective (cardioselective) adrenergic antagonist, is similar to atenolol in its moderate lipid solubility, lack of intrinsic sympathomimetic activity (ISA), and weak membrane stabilizing activity (MSA).
Mechanism of Action
Like betaxolol and atenolol, metoprolol competes with adrenergic neurotransmitters such as catecholamines for binding at beta(1)-adrenergic receptors in the heart and vascular smooth muscle. Beta(1)-receptor blockade results in a decrease in heart rate, cardiac output, and blood pressure.
Absorption
Rapid and complete, 50%
Toxicity
LD50=5500 mg/kg (orally in rats), toxic effects include bradycardia, hypotension, bronchospasm, and cardiac failure. LD50=2090 mg/kg (orally in mice)
Biotrnasformation / Drug Metabolism
Primarily hepatic
Contraindications
Hypertension and Angina: Extended release metoprolol succinate is contraindicated in sinus
bradycardia, heart block greater than first degree, cardiogenic shock, and overt cardiac failure
Drug Interactions
Catecholamine-depleting drugs (e.g., reserpine) may have an additive effect when given with beta-blocking
agents. Patients treated with extended release metoprolol succinate plus a catecholamine depletor should therefore be
closely observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural
hypotension.
|