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.

ADJUST DOSING INTERVAL: Bowel cleansing products can increase the gastrointestinal transit rate. Oral medications administered within one hour of the start of administration of the bowel cleansing solution may be flushed from the gastrointestinal tract and not properly absorbed.

MANAGEMENT: Patients should be advised that absorption of oral medications may be impaired during bowel cleansing treatment. Oral medications (e.g., anticonvulsants, oral contraceptives, antidiabetic agents, antibiotics) should not be administered during and within one hour of starting bowel cleansing treatment whenever possible. However, if concomitant use cannot be avoided, monitoring for reduced therapeutic effects may be advisable.

GENERALLY AVOID: Use of anticholinergic agents with alcohol may result in sufficient impairment of attention so as to render driving and operating machinery more hazardous. In addition, the potential for abuse may be increased with the combination. The mechanism of interaction is not established but may involve additive depressant effects on the central nervous system. No effect of oral propantheline or atropine on blood alcohol levels was observed in healthy volunteers when administered before ingestion of a standard ethanol load. However, one study found impairment of attention in subjects given atropine 0.5 mg or glycopyrrolate 1 mg in combination with alcohol.

MANAGEMENT: Alcohol should generally be avoided during therapy with anticholinergic agents. Patients should be counseled to avoid activities requiring mental alertness until they know how these agents affect them.