Drug interactions: Epinephrine must not be administered concomitantly with other sympathomimetic drugs (such as isoproterenol) because of possible additive effects and increased toxicity. Combined effects may induce serious cardiac arrhythmias. They may be administered alternately when the preceding effect of other such drugs has subsided.
Epinephrine is readily destroyed by alkalies and oxidizing agents (e.g., oxygen, chlorine, bromine, iodine, permanganates, chromates, nitrites, and salts of easily reducible metals, especially iron).
The effects of epinephrine may be potentiated by tricyclic antidepressants, certain antihistamines (e.g., diphenhydramine, tripelennamine, chlorpheniramine) and sodium I-thyroxine.
In obstetrics, if vasopressor drugs are used either to correct hypotension or added to the local anesthetic solution, some oxytocic drugs may cause severe persistent hypertension; even rupture of a cerebral blood vessel may occur during the postpartum period.
All vasopressors should be used cautiously in patients taking monoamine oxidase (MAO) inhibitors.
Cyclopropane or halogenated hydrocarbon anesthetics such as halothane which sensitize the myocardium may induce cardiac arrhythmia. (See Contraindications.) When encountered, such arrhythmias may respond to administration of a beta-adrenergic blocking drug.
Diruretic agents may decrease vascular response to pressor drugs such as epinephrine.
Epinephrine may antagonize the neuron blockade produced by guanethidine resulting in decreased antihypertensive effect and requiring increased dosage of the latter.
Use of epinephrine with excessive doses of digitalis, mercurial diuretics or other drugs that sensitize the heart to arrhythmias is not recommended.
Rapidly acting vasodilators such as nitrites or alpha-blocking agents may counteract the marked pressor effects of epinephrine.
Propranolol administered concomitantly with epinephrine may block the beta-adrenergic effects of epinephrine, causing hypertension.