IMPORTANT SAFETY INFORMATION
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Lopressor® (metoprolol tartrate) 50mg and 100mg Tablets
Lopressor® (metoprolol tartrate) Tablets are contraindicated in patients with hypertension and angina, particularly in sinus bradycardia, certain types of heart blockages (greater than first degree), cardiogenic shock, and obvious cardiac failure. Hypersensitivity to Lopressor and related derivatives, or to any of the excipients, or to other beta blockers can occur.
Sick sinus syndrome, which may result in irregular heartbeat, can occur, as can severe peripheral arterial circulatory disorders.
Lopressor is contraindicated in patients having a heart rate <45 beats per minute; second and third-dress heart block; significant first degree heart block(P-R interval > 0.24 sec), systolic blood pressure <100mmHg, or moderate-to-severe heart failure.
WARNINGS AND PRECAUTIONS
Beta blockers, like Lopressor, may precipitate heart failure and cardiogenic shock. If this occurs, it may be necessary to lower the dose of Lopressor or discontinue it.
Ischemic Heart Disease
Do not abruptly discontinue Lopressor therapy in patients with coronary artery disease. Severe exacerbation of angina, myocardial infarction and ventricular arrhythmias have been reported in patients with coronary artery disease following the abrupt discontinuation of therapy with beta-blockers. When discontinuing chronically administered Lopressor, particularly in patients with coronary artery disease, the dosage should be gradually reduced over a period of 1-2 weeks and the patient should be carefully monitored. If angina markedly worsens or acute coronary insufficiency develops, Lopressor administration should be reinstated promptly, at least temporarily, and other measures appropriate for the management of unstable angina should be taken. Patients should be warned against interruption or discontinuation of therapy without the physician’s advice. Because coronary artery disease is common and may be unrecognized, it may be prudent not to discontinue Lopressor therapy abruptly even in patients treated only for hypertension.
Use During Major Surgery
Chronically administered beta-blocking therapy should not be withdrawn prior to major surgery; however, the impaired ability of the heart to respond to reflex adrenergic stimuli may increase the risks of general anesthesia and surgical procedures.
Bradycardia, including sinus pause, heart block, and cardiac arrest have occurred with the use of Lopressor. Patients with first-degree atrioventricular block, sinus node dysfunction, or conduction disorders may be at increased risk.
Exacerbation of Bronchospastic Disease
Patients with bronchospastic disease should not generally receive beta blockers. However, because of its relative beta1 selectivity, Lopressor may be used in patients with bronchospastic disease who do not respond to, or who cannot tolerate, other antihypertensive treatment.
Diabetes and Hypoglycemia
Beta blockers may mask tachycardia occurring with hypoglycemia, but other manifestations such as dizziness and sweating may not be significantly affected.
If Lopressor is used in the setting of pheochromocytoma, it should be given in combination with an alpha blocker, and only after the alpha blocker has been initiated.
Lopressor may mask certain clinical signs (e.g., tachycardia) of hyperthyroidism. Avoid abrupt withdrawal of beta blockade, which might precipitate a thyroid storm.
Risk of Anaphylactic Reactions
While taking beta blockers, patients with a history of severe anaphylactic reaction to a variety of allergens may be more reactive to repeated challenge, either accidental, diagnostic, or therapeutic. Such patients may be unresponsive to the usual doses of epinephrine used to treat allergic reaction.
Catecholamine-depleting drugs (e.g., reserpine) may have an additive effect when given with beta-blocking agents or monoamine oxidase (MAO) inhibitors. Both digitalis glycosides and beta blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia. Concomitant administration of a beta-adrenergic antagonist with a calcium channel blocker may produce an additive reaction in myocardial contractility because of negative chronotropic and inotropic effects. Potent inhibitors of the CYP2D6 enzyme may increase plasma concentration of Lopressor. Concomitant administration of hydralazine may inhibit presystemic metabolism of metoprolol leading to increased concentrations of metoprolol. Lopressor may increase the hypertensive effects of alpha-adrenergic blockers. Concomitant administration with beta-blockers may enhance the vasoconstrictive action of ergot alkaloids. In general, administration of beta-blockers should be withheld before dipyridamole testing, with careful monitoring of heart rate following the dipyridamole injection.
Pregnancy Category C
Upon confirming the diagnosis of pregnancy, women should immediately inform their doctor. The amount of data on the use of Lopressor in pregnant women is limited. Lopressor is excreted in breast milk in very small quantities.
Pediatric and Geriatric use of Lopressor has not been studied.
Hypertension and Angina: Most adverse effects have been mild and transient.
Central Nervous System: Tiredness and dizziness have occurred in about 10% of patients.
Cardiovascular: Shortness of breath and bradycardia has occurred in about 3% of patients.
Respiratory: Wheezing and dyspnea have been reported in about 1% of patients.
Gastrointestinal: Diarrhea has occurred in about 5% of patients.
Hypersensitive Reactions: Pruritis or rash has occurred in about 5% of patients.
Acute Toxicity: Several cases of overdosage have been reported, some leading to death.
Signs and Symptoms: Potential signs and symptoms associated with Lopressor overdose are bradycardia, hypotension, bronchospasm, myocardial infarction, cardiac failure and death. There is no specific antidote.