Dyspnea of pulmonary origin has been reported in fewer than 1 of 100 patients.
Nausea and abdominal pain have been reported in fewer than 1 of 100 patients.
Rash and worsened psoriasis have been reported, but a drug relationship is not clear.
Unstable diabetes and claudication have been reported, but a drug relationship is not clear.
A variety of adverse reactions not listed above have been reported with other beta-adrenergic blocking agents and should be considered potential adverse reactions to metoprolol.
Reversible mental depression progressing to catatonia; an acute reversible syndrome characterized by disorientation for time and place, short-term memory loss, emotional lability, slightly clouded sensorium, and decreased performance on neuropsychometrics.
Intensification of AV block (see CONTRAINDICATIONS).
Agranulocytosis, nonthrombocytopenic purpura and thrombocytopenic purpura.
Fever combined with aching and sore throat, laryngospasm and respiratory distress.
The following adverse reactions have been reported during post-approval use of metoprolol: confusional state, an increase in blood triglycerides and a decrease in High Density Lipoprotein (HDL). Because these reports are from a population of uncertain size and are subject to confounding factors, it is not possible to reliably estimate their frequency.
Several cases of overdosage have been reported, some leading to death.
Oral LD 50 ’s (mg/kg): mice, 1,158 to 2,460; rats, 3,090 to 4,670.
Potential signs and symptoms associated with overdosage with metoprolol are bradycardia, hypotension, bronchospasm, myocardial infarction, cardiac failure and death.
There is no specific antidote.
In general, patients with acute or recent myocardial infarction may be more hemodynamically unstable than other patients and should be treated accordingly (see WARNINGS: Myocardial Infarction).
On the basis of the pharmacologic actions of metoprolol, the following general measures should be employed:
Gastric lavage should be performed.
Other clinical manifestations of overdose should be managed symptomatically based on modern methods of intensive care.
Administer a vasopressor, e.g., norepinephrine or dopamine.
Administer a beta 2 -stimulating agent and/or a theophylline derivative.
Administer digitalis glycoside and diuretic. In shock resulting from inadequate cardiac contractility, consider administration of dobutamine, isoproterenol or glucagon.
Individualize the dosage of metoprolol tartrate tablets. Metoprolol tartrate tablets should be taken with or immediately following meals.
The usual initial dosage of metoprolol tartrate tablets is 100 mg daily in single or divided doses, whether used alone or added to a diuretic. Increase the dosage at weekly (or longer) intervals until optimum blood pressure reduction is achieved. In general, the maximum effect of any given dosage level will be apparent after one week of therapy. The effective dosage range of metoprolol tartrate tablets is 100 mg per day to 450 mg per day. Dosages above 450 mg per day have not been studied. While once daily dosing is effective and can maintain a reduction in blood pressure throughout the day, lower doses (especially 100 mg) may not maintain a full effect at the end of the 24-hour period, and larger or more frequent daily doses may be required. This can be evaluated by measuring blood pressure near the end of the dosing interval to determine whether satisfactory control is being maintained throughout the day. Beta 1 selectivity diminishes as the dose of metoprolol tartrate tablets is increased.
The dosage of metoprolol tartrate tablets should be individualized. Metoprolol tartrate tablets should be taken with or immediately following meals.
The usual initial dosage of metoprolol tartrate tablets is 100 mg daily, given in two divided doses. Gradually increase the dosage at weekly intervals until optimum clinical response has been obtained or there is pronounced slowing of the heart rate. The effective dosage range of metoprolol tartrate tablets is 100 mg per day to 400 mg per day. Dosages above 400 mg per day have not been studied. If treatment is to be discontinued, gradually decrease the dosage over a period of 1 to 2 weeks (see WARNINGS).
During the early phase of definite or suspected acute myocardial infarction, initiate treatment with metoprolol tartrate tablets as soon as possible after the patient’s arrival in the hospital. Such treatment should be initiated in a coronary care or similar unit immediately after the patient’s hemodynamic condition has stabilized.
Begin treatment in this early phase with the intravenous administration of three bolus injections of 5 mg of metoprolol tartrate each; give the injections at approximately 2 minute intervals. During the intravenous administration of metoprolol, monitor blood pressure, heart rate, and electrocardiogram.
In patients who tolerate the full intravenous dose (15 mg), initiate metoprolol tartrate tablets, 50 mg every 6 hours, 15 minutes after the last intravenous dose and continue for 48 hours. Thereafter, the maintenance dosage is 100 mg twice daily (see Late Treatment below).
Start patients who appear not to tolerate the full intravenous dose on metoprolol tartrate tablets either 25 mg or 50 mg every 6 hours (depending on the degree of intolerance) 15 minutes after the last intravenous dose or as soon as their clinical condition allows. In patients with severe intolerance, discontinue metoprolol tartrate tablets (see WARNINGS).
Start patients with contraindications to treatment during the early phase of suspected or definite myocardial infarction, patients who appear not to tolerate the full early treatment, and patients in whom the physician wishes to delay therapy for any other reason on metoprolol tartrate tablets, 100 mg twice daily, as soon as their clinical condition allows. Continue therapy for at least 3 months. Although the efficacy of metoprolol beyond 3 months has not been conclusively established, data from studies with other beta-blockers suggest that treatment should be continued for 1 to 3 years.
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