Metoprolol precautions

# List of Precautions
General
Information for Patients
Patients should be advised
Drug Interactions
Risk of Anaphylactic Reaction
General Anesthetics
CYP2D6 Inhibitors
Clonidine
Carcinogenesis, Mutagenesis, Impairment of Fertility
Nursing Mothers
Pediatric Use
Geriatric Use

## General
Metoprolol should be used with caution in patients with impaired hepatic function.
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## Information for Patients
Patients should be advised to take Metoprolol regularly and continuously, as directed, with or immediately following meals. If a dose should be missed, the patient should take only the next scheduled dose (without doubling it). Patients should not discontinue Metoprolol without consulting the physician.
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## Patients should be advised
- (1) to avoid operating automobiles and machinery or engaging in other tasks requiring alertness until the patients response to therapy with Metoprolol has been determined;
- (2) to contact the physician if any difficulty in breathing occurs;
- (3) to inform the physician or dentist before any type of surgery that he or she is taking Metoprolol.
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## Drug Interactions
Catecholamine-depleting drugs (e.g., reserpine) may have an additive effect when given with beta-blocking agents. Patients treated with Metoprolol plus a catecholamine depletor should therefore be closely observed for evidence of hypotension or marked bradycardia, which may produce vertigo, syncope, or postural hypotension.
Both digitalis glycosides and beta-blockers slow atrioventricular conduction and decrease heart rate. Concomitant use can increase the risk of bradycardia.
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## Risk of Anaphylactic Reaction
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.
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## General Anesthetics
Some inhalation anesthetics may enhance the cardiodepressant effect of beta-blockers (see WARNINGS, Major Surgery).
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## CYP2D6 Inhibitors
Potent inhibitors of the CYP2D6 enzyme may increase the plasma concentration of Metoprolol.
Strong inhibition of CYP2D6 would mimic the pharmacokinetics of CYP2D6 poor metabolizer (see  Pharmacokinetics section). Caution should therefore be exercised when co-administering potent CYP2D6 inhibitors with Metoprolol. Known clinically significant potent inhibitors of CYP2D6 are antidepressants such as fluoxetine, paroxetine or bupropion, antipsychotics such as thioridazine, antiarrhythmics such as quinidine or propafenone, antiretrovirals such as ritonavir, antihistamines such as diphenhydramine, antimalarials such as hydroxychloroquine or quinidine, antifungals such as terbinafine and medications for stomach ulcers such as cimetidine.
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## Clonidine
If a patient is treated with clonidine and Metoprolol concurrently, and clonidine treatment is to be discontinued, Metoprolol should be stopped several days before clonidine is withdrawn. Rebound hypertension that can follow withdrawal of clonidine may be increased in patients receiving concurrent beta-blocker treatment.
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## Carcinogenesis, Mutagenesis, Impairment of Fertility
Long-term studies in animals have been conducted to evaluate carcinogenic potential. In a 2-year study in rats at three oral dosage levels of up to 800 mg/kg per day, there was no increase in the development of spontaneously occurring benign or malignant neoplasms of any type. The only histologic changes that appeared to be drug related were an increased incidence of generally mild focal accumulation of foamy macrophages in pulmonary alveoli and a slight increase in biliary hyperplasia. In a 21-month study in Swiss albino mice at three oral dosage levels of up to 750 mg/kg per day, benign lung tumors (small adenomas) occurred more frequently in female mice receiving the highest dose than in untreated control animals. There was no increase in malignant or total (benign plus malignant) lung tumors, nor in the overall incidence of tumors or malignant tumors. This 21-month study was repeated in CD-1 mice, and no statistically or biologically significant differences were observed between treated and control mice of either sex for any type of tumor.
All mutagenicity tests performed (a dominant lethal study in mice, chromosome studies in somatic cells, a Salmonella/mammalian-microsome mutagenicity test, and a nucleus anomaly test in somatic interphase nuclei) were negative.
No evidence of impaired fertility due to Metoprolol was observed in a study performed in rats at doses up to 55.5 times the maximum daily human dose of 450 mg.
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## Pregnancy
Pregnancy Category C
Metoprolol has been shown to increase postimplantation loss and decrease neonatal survival in rats at doses up to 55.5 times the maximum daily human dose of 450 mg. Distribution studies in mice confirm exposure of the fetus when Metoprolol is administered to the pregnant animal. These studies have revealed no evidence of impaired fertility or teratogenicity. There are no adequate and well-controlled studies in pregnant women. Because animal reproduction studies are not always predictive of human response, this drug should be used during pregnancy only if clearly needed.
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## Nursing Mothers
Metoprolol is excreted in breast milk in a very small quantity. An infant consuming 1 liter of breast milk daily would receive a dose of less than 1 mg of the drug. Caution should be exercised when Metoprolol is administered to a nursing woman.
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## Pediatric Use
Safety and effectiveness in pediatric patients have not been established.
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## Geriatric Use
Clinical trials of Metoprolol in hypertension did not include sufficient numbers of elderly patients to determine whether patients over 65 years of age differ from younger subjects in their response to Metoprolol. Other reported clinical experience in elderly hypertensive patients has not identified any difference in response from younger patients.
In worldwide clinical trials of Metoprolol in myocardial infarction, where approximately 478 patients were over 65 years of age (0 over 75 years of age), no age-related differences in safety and effectiveness were found. Other reported clinical experience in myocardial infarction has not identified differences in response between the elderly and younger patients. However, greater sensitivity of some elderly individuals taking Metoprolol cannot be categorically ruled out. Therefore, in general, it is recommended that dosing proceed with caution in this population.
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Adapted from the FDA Package Insert.