Drug Interaction Report

In one study, after treatment with ephedrine, a 36% decrease in mean dexamethasone half-life and a 42% increase in the clearance of plasma dexamethasone has been reported. The mechanism of this interaction has not been reported. The authors of the study recommend caution when prescribing ephedrine for asthmatics requiring long term therapy with dexamethasone. The authors of the study further suggest that since ephedrine accelerates labeled dexamethasone clearance while theophylline did not, theophylline may be a more appropriate bronchodilator to use in this patient population.

MONITOR: Coadministration of two or more sympathomimetic agents may increase the risk of adverse effects such as nervousness, irritability, and increased heart rate. Central nervous system (CNS) stimulants, particularly amphetamines, can potentiate the adrenergic response to vasopressors and other sympathomimetic agents. Additive increases in blood pressure and heart rate may occur due to enhanced peripheral sympathetic activity.

MANAGEMENT: Caution is advised if two or more sympathomimetic agents are coadministered. Pulse and blood pressure should be closely monitored.