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Cautions

Contraindications

• Patients with sinus bradycardia, heart block greater than 1st degree, cardiogenic shock, overt or decompensated cardiac failure, or sick sinus syndrome (unless a permanent pacemaker is in place).
• Patients with AMI who have a heart rate <45 bpm, heart block greater than 1st degree, systolic BP <100 mm Hg, or moderate to severe cardiac failure.

Warnings/Precautions

Warnings

Abrupt Withdrawal of Therapy

Abrupt discontinuance may exacerbate angina symptoms or precipitate MI in patients with CAD. Avoid abrupt discontinuance. Gradually decrease dosage over 1–2 weeks and monitor patients carefully. If exacerbation of angina occurs or acute coronary insufficiency develops, reinstitute therapy promptly, at least temporarily, and initiate appropriate measures for the management of unstable angina.

Cardiac Failure

Possible precipitation of CHF; possible decreased exercise tolerance in patients with left ventricular dysfunction.

Initiate therapy and subsequent dosage adjustments in patients with CHF under close medical supervision. Prior to initiation of metoprolol, stabilize patient on other therapy (e.g., ACE inhibitor, diuretic, and/or cardiac glycoside). Symptomatic improvement may not be evident for 2–3 months after initiating therapy.

Avoid use in patients with decompensated CHF; use cautiously in patients with inadequate myocardial function and, if necessary, in patients with well-compensated heart failure (e.g., those controlled with ACE inhibitors, cardiac glycosides, and/or diuretics); use with extreme caution in patients with substantial cardiomegaly.

Adequate treatment (e.g., with a cardiac glycoside and/or diuretic) and close observation recommended if signs or symptoms of impending cardiac failure occur; if cardiac failure continues, discontinue therapy, gradually if possible.

Bronchospastic Disease

Possible bronchoconstriction, especially at dosages >100 mg daily.

Use with caution in patients with bronchospastic disease; administer lowest effective dosage (initially in 3 divided doses) and with maximal therapy with a β₂-adrenergic agonist.

Bradycardia

Possible bradycardia and depressed SA node automaticity.

Carefully monitor hemodynamic status of patients with MI; use with caution in patients with sinus node dysfunction.

If heart rate < 40 bpm with evidence of decreased cardiac output, administer IV atropine; if bradycardia is refractory to atropine, discontinue metoprolol and consider cautious administration of isoproterenol or use of a cardiac pacemaker.

AV Block

Possible intensification of AV block, AV dissociation, complete heart block, or cardiac arrest, especially in patients with preexisting heart block caused by digoxin or other factors.

Use with caution, if at all, in patients with AV conduction defects.

If heart block occurs in patients with MI, discontinue metoprolol and administer IV atropine; if the heart block is refractory to atropine, consider cautious administration of isoproterenol or use of a cardiac pacemaker.

Hypotension

If hypotension (systolic BP <90 mm Hg) occurs in patients with MI, discontinue metoprolol and assess hemodynamic status and extent of myocardial damage. Invasive monitoring of central venous, pulmonary capillary wedge, and arterial pressures may be necessary; appropriate therapy with IV fluids and other treatment modalities recommended.

If hypotension is associated with severe bradycardia or heart block, provide treatment directed at reversing these. (See Bradycardia and also AV Block under Cautions.)

Major Surgery

Possible increased risks associated with general anesthesia (e.g., severe hypotension, maintenance of heart beat) due to decreased ability of the heart to respond to reflex β-adrenergic stimuli.

Use with caution in patients undergoing major surgery involving general anesthesia; avoid use of anesthetics that cause myocardial depression (see Specific Drugs under Interactions).

Diabetes and Hypoglycemia

Possible decreased signs and symptoms of hypoglycemia (e.g., tachycardia, palpitation, BP changes, tremor, feelings of anxiety) and increased insulin-induced hypoglycemia.

Use with caution in patients with diabetes mellitus.

Thyrotoxicosis

Signs of hyperthyroidism (e.g., tachycardia) may be masked. Possible thyroid storm if therapy is abruptly withdrawn; carefully monitor patients having or suspected of developing thyrotoxicosis.

General Precautions

Ocular Effects

Possible dry eyes and decreased tear production, minimal injection of conjunctivae and/or eyelids, punctate keratitis, keratoconjunctivitis or corneal ulceration. Close observation recommended.

Possible Prescribing and Dispensing Errors

Ensure accuracy of prescription; similarity in spelling between Toprol-XL^® (metoprolol succinate) and Topamax^® (trade name for topiramate, an anticonvulsant and antimigraine agent) may result in errors.

Potential also exists for dispensing errors involving confusion between Toprol-XL^® and Tegretol^® or Tegretol^®-XR (trade names for carbamazepine, an anticonvulsant also used for relief of pain associated with trigeminal neuralgia, as well as for various psychiatric disorders).

These medication errors have been associated with serious adverse events sometimes requiring hospitalization as a result of either lack of the intended medication (e.g., seizure recurrence, return of hallucinations, suicide attempt, hypertension recurrence) or exposure to the wrong drug (e.g., bradycardia in a patient erroneously receiving metoprolol).

Use of Fixed Combinations

When used in fixed combination with hydrochlorothiazide, consider the cautions, precautions, and contraindications associated with hydrochlorothiazide.

Specific Populations

Pregnancy

Category C.

Lactation

Distributed into milk. Use with caution.

Pediatric Use

Safety and efficacy remain to be fully established in children; however, some experts have recommended dosages for hypertension based on current limited clinical experience.

Geriatric Use

Among patients with heart failure, safety and efficacy profiles in geriatric individuals are similar to those in younger adults.

BP determinations recommended in both the seated position and after patient stands quietly for 2–5 minutes (to recognize postural hypotension).

Hepatic Impairment

Hepatic elimination; use with caution.

Common Adverse Effects

Dizziness, tiredness, insomnia, gastric upset.