metoprolol, Lopressor, Toprol XL (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

WARNING: In patients with existing slow heart rates (bradycardias) and heart blocks (defects in the electrical conduction of the heart), metoprolol can cause dangerously slow heart rates, and even shock. Metoprolol reduces the force of heart muscle contraction and can aggravate symptoms of heart failure. In patients with coronary artery disease, abruptly stopping metoprolol can suddenly worsen angina, and occasionally precipitate heart attacks. If it is necessary to discontinue metoprolol, its dosage should be reduced gradually over several weeks.

Initiation of high-dose extended release metoprolol in patients undergoing non-cardiac surgery is associated with bradycardia (slow heart rate), hypotension, stroke, and death. However, long-term therapy with metoprolol should not be routinely withdrawn prior to major surgery. Impaired ability of the heart to respond to reflex adrenergic stimuli may increase the risks of general anesthesia and surgery.

PRESCRIPTION: Yes

GENERIC AVAILABLE: Yes

PREPARATIONS: Tablets: 25, 50, and 100 mg. Tablets (extended release): 25, 50, 100, and 200 mg. Injection: 1 mg/ml

STORAGE: Tablets should be stored between 15 C to 30 C (59 F  to 86 F). They should be protected from moisture and dispensed in tight, light-resistant containers.

DOSING: Metoprolol should be taken before meals or at bedtime.

  • The dose for treating hypertension is 100-450 mg daily in single or divided doses.
  • Angina is treated with 100-400 mg daily in two divided doses.
  • Heart attack (acute myocardial infarction) is treated with three 5 mg injections administered 2 minutes apart followed by treatment with 50 mg oral metoprolol every 6 hours for 48 hours. After 48 hours, patients should receive 100 mg orally twice daily for at least 3 months.
  • The dose for congestive heart failure is 25 mg/daily initially. Then the dose is increased every 2 weeks to reach a target dose of 200 mg/daily orally.
  • Hyperthyroidism is treated with 25 to 30 mg by mouth every 6 hours.

DRUG INTERACTIONS: Calcium channel blockers and digoxin (Lanoxin) can lower blood pressure and heart rate to dangerous levels when administered together with metoprolol.

Medically Reviewed by a Doctor on 12/3/2014


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