Drug Interaction Report

CONTRAINDICATED: By inhibiting the breakdown of catecholamines, monoamine oxidase inhibitors (MAOIs) may theoretically potentiate the cardiovascular effects of systemically absorbed sympathomimetic agents following topical administration (e.g., nasal decongestants, ophthalmic vasoconstrictors). However, the interaction has not been reported extensively in the medical literature. No increase in blood pressure or heart rate was observed when tranylcypromine was administered to a patient using 1% epinephrine eye drop twice a day. Most topical decongestants and vasoconstrictors are direct-acting sympathomimetics, which appear to be less affected by MAOIs than indirect- or mixed-acting sympathomimetics such as pseudoephedrine or ephedrine. While MAOI use has been reported to precipitate severe hypertensive reactions and hyperpyrexia in patients receiving indirect- or mixed-acting agents, most studies have found minimal effect on pressor response to systemically administered direct-acting agents including epinephrine, norepinephrine, and isoproterenol. Nevertheless, increased pressor effects and greater than 50% reductions in the required dosage of direct-acting agents have been reported in hypertensive patients who were being treated for MAOI-induced postural hypotension. There have also been occasional reports of increased blood pressure and heart rate in patients receiving systemic direct-acting agents and MAOIs.

MANAGEMENT: Concomitant use of tetrahydrozoline nasal formulations with MAOIs or other agents that possess MAOI activity (e.g., furazolidone, linezolid, methylene blue, procarbazine) is considered contraindicated by the manufacturers.