PREPARATIONS: Tablets: 25, 50, and 100 mg. Tablets (extended release): 25, 50, 100, and 200 mg. Injection: 1 mg/ml
PREGNANCY AND BREASTFEEDING SAFETY: Safe use of metoprolol during pregnancy has not been established.
Small quantities of metoprolol are excreted in breast milk and may potentially cause adverse effects in the infant.
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 CLASS AND MECHANISM: Metoprolol is a beta-adrenergic blocking agent that is used for treating high blood pressure, heart pain, abnormal rhythms of the heart, and some neurologic conditions. Examples of beta-adrenergic blockers include propanolol (Inderal, Inderal LA, Innopran XL), atenolol (Tenormin), and timolol (Blocadren). Metoprolol blocks the action of the sympathetic nervous system, a portion of the involuntary nervous system, by blocking beta receptors on sympathetic nerves. Since the sympathetic nervous system is responsible for increasing the rate with which the heart beats, by blocking the action of these nerves metoprolol reduces the heart rate and is useful in treating abnormally rapid heart rhythms.
Metoprolol also reduces the force of contraction of heart muscle and thereby lowers blood pressure. By reducing the heart rate and the force of muscle contraction, metoprolol reduces the need for oxygen by heart muscle. Since heart pain (angina pectoris) occurs when oxygen demand of the heart muscle exceeds the supply of oxygen, metoprolol, by reducing the demand for oxygen, is helpful in treating heart pain. The FDA approved metoprolol in August 1978.
Medically reviewed by Eni Williams, PharmD
Reference: FDA Prescribing Information
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