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Back to Cardiology Drug index

Back to Beta Blockers

Metoprolol tartrate - Lopressor,
Toprol XL

Pregnancy Category B

Drug classes
Beta-adrenergic blocking agent (alpha 1-selective)
Antihypertensive agent

Mechanism of action
Competitively blocks beta-adrenergic receptors in the heart and juxtoglomerular apparatus. They lead to decreased heart rate decreasing the work load by the heart. They do not produce coronary vasodilatation but lead to a shift and redistribution of coronary circulation to the ischemic areas. It decreases the release of renin from the kidney, thus lowering blood pressure. Acts in the CNS to reduce sympathetic outflow and vasoconstrictor tone.

Hypertension, alone or with other drugs, especially diuretics
Prevention of reinfarction in MI patients who are hemodynamically stable
or within 3-10 d of the acute MI
Treatment of angina pectoris

Contraindicated in the presence of sinus bradycardia (heart block greater than 1st degree), cardiogenic shock, CHF.

Adverse effects
CNS: Nystagmus, ataxia, dysarthria, slurred speech, mental confusion, dizziness, drowsiness, insomnia, transient nervousness, motor twitchings,fatigue, irritability, depression, numbness, tremor, headache, photophobia, diplopia, conjunctivitis
GI: Nausea, vomiting, diarrhea, constipation, gingival hyperplasia, toxic hepatitis, liver damage, sometimes fatal; hypersensitivity reactions with hepatic involvement, including hepatocellular degeneration and fatal hepatocellular necrosis
Respiratory: Pulmonary fibrosis, acute pneumonitis
Hematologic: Hematopoietic complications, sometimes fatal: thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, pancytopenia; macrocytosis and megaloblastic anemia that usually respond to folic acid therapy; eosinophilia, monocytosis, leukocytosis, simple
anemia, hemolytic anemia, aplastic anemia, hyperglycemia
: Nephrosis
Dermatologic: Dermatologic reactions, scarlatiniform, morbilliform, maculopapular, urticarial and nonspecific rashes; serious and sometimes fatal dermatologic reactions-bullous, exfoliative, or purpuric dermatitis, lupus erythematosus, and Stevens-Johnson syndrome; toxic epidermal necrolysis, hirsutism, alopecia, coarsening of the facial
features, enlargement of the lips, Peyronie's disease
: Lymph node hyperplasia, sometimes progressing to frank malignant
lymphoma, monoclonal gammopathy and multiple myeloma (prolonged therapy),  polyarthropathy, osteomalacia, weight gain, chest pain, periarteritis nodosa
IV use complications: Hypotension, transient hyperkinesia, drowsiness, nystagmus, circumoral tingling, vertigo, nausea, cardiovascular collapse, CNS depression

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