Metoprolol

A to Z Drug Facts

 Action Blocks beta receptors, primarily affecting cardiovascular system (decreases heart rate, decreases contractility, decreases BP) and lungs (promotes bronchospasm).

 Indications Used alone or in combination with other antihypertensive agents, for management of hypertension, long-term management of angina pectoris, myocardial infarction (immediate-release tablets and injection).

 Contraindications Greater than first-degree heart block; congestive heart failure unless secondary to tachyarrhythmia treatable with beta-blockers; overt or moderate to severe cardiac failure; sinus bradycardia; cardiogenic shock; hypersensitivity to beta-blockers; systolic blood pressure < 100 mm/Hg; MI in patients with heart rate < 45 beats/min.

 Route/Dosage

Hypertension

ADULTS: PO 100 mg/day in single or divided doses initially; maintenance: 100–450 mg/day.

Angina

ADULTS: PO 100 mg/day in 2 divided doses initially; maintenance: 100–400 mg/day.

Myocardial Infarction

ADULTS: IV bolus injection 5 mg slowly; may repeat every 2 min up to total of 15 mg. If tolerated, give PO 50 mg q 6 hr beginning 15 min after last IV dose; continue for 48 hr followed by PO 100 mg bid for 1–3 mo. If patient is intolerant of full IV dose, give PO 25–50 mg q 6 hr starting 15 min after last IV dose.

 Interactions

Barbiturates: Bioavailability of metoprolol may decrease. Cimetidine: May increase metoprolol levels. Clonidine: May enhance or reverse antihypertensive effect; potentially life-threatening situations may occur, especially on abrupt withdrawal of clonidine. Hydralazine: Serum levels of both drugs may increase. Lidocaine: Lidocaine levels may increase, leading to toxicity. NSAIDs: Some agents may impair antihypertensive effect. Prazosin: Orthostatic hypotension may increase. Propafenone, quinidine, thioamines: Effects of metoprolol may increase. Rifampin: May decrease effects of metoprolol. Verapamil: Effects of both drugs may be increased.

 Lab Test Interferences Antinuclear antibodies may develop but are usually reversible on discontinuation.

 Adverse Reactions

CV: Hypotension; edema; flushing; bradycardia. CNS: Headache; fatigue; dizziness; depression; lethargy; drowsiness; forgetfulness; leepiness; vertigo; paresthesias. DERM: Rash; facial erythema; alopecia; urticaria; pruritus. EENT: Dry eyes; visual disturbances. GI: Nausea; vomiting; diarrhea. GU: Impotence; urinary retention; difficulty with urination. RESP: Bronchospasm; dyspnea; wheezing. OTHER: Increased hypoglycemic response to insulin; may mask hypoglycemic signs; uscle cramps; asthenia; systemic lupus erythematosus.

 Precautions

Pregnancy: Category C. Lactation: Excreted in breast milk. Children: Safety and efficacy not established. Anaphylaxis: Deaths have occurred; aggressive therapy may be required. AV block: Slows AV conduction and may cause heart block. Bradycardia: Metoprolol decreases heart rate in most patients. Congestive heart failure: Administer cautiously in CHF patients controlled by digitalis and diuretics. Notify physician at first sign or symptom of CHF or of unexplained respiratory symptoms in any patient. Peripheral vascular disease: May precipitate or aggravate symptoms of atrial insufficiency. Renal/hepatic function impairment: Reduced daily dose advised. Thyrotoxicosis: May mask clinical signs (eg, tachycardia) of developing or continuing hyperthyroidism. Abrupt withdrawal may exacerbate symptoms of hyperthyroidism, including thyroid storm.

 Administration/Storage

• Tablets (immediate release) and injection: ive at same time every day.
• When switching from immediate-release tablets, give same total daily dose.
• Give drug at same time consistently with or without meals. Food slightly enhances drug's bioavailability.
• Store at room temperature and protect from light.

 Assessment/Interventions

• Obtain patient history, including drug history and any known allergies.
• Implement periodic ECG or telemetry monitoring, as ordered, if bradyarrhythmias occur.
• Check BP and pulse every 8 hours.
• Monitor levels of BUN, LDH and uric acid and glucose tolerance.
• In diabetic patients, monitor blood sugar closely.
• Notify physician of CNS changes, unstable diabetes, rash, pruritus, visual disturbance or eye irritation, dyspnea, bronchospasm, asthma, arthralgia, muscle cramps.
• Avoid abrupt withdrawal of therapy, which may precipitate ventricular arrhythmia, angina, MI, death.
• Assess peripheral pulses for evidence of arterial occlusion.

 Patient/Family Education

• Teach patient how to check pulse and BP.
• Advise patient to contact physician if pulse is < 50 bpm.
• Explain why medication should not be discontinued abruptly.
• Tell patient to check blood sugar regularly and consult physician if levels are unstable.
• Explain that adverse effects are usually mild and transient and will generally subside with continued therapy.
• Instruct patient to report these symptoms to physician: difficulty breathing, night cough or edema.
• Advise patient that drug may cause drowsiness and to use caution while driving or performing tasks requiring mental alertness.
• Instruct patient not to take otc cold preparations without consulting physician.

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Copyright © 2003 Facts and Comparisons
David S. Tatro
A to Z Drug Facts