The Effects of Ephedrine and Theophylline on Dexamethasone Metabolism in Bronchial Asthma

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Abstract
The effect of ephedrine (9 patients) and theophylline (7 patients) on dexamethasone metabolism was studied before and after 3 wk of drug therapy in 16 asthmatics. Five patients were studied similarily but treated with placebo. After treatment with ephedrine, there was a mean decrease in plasma dexamethasone half-life (t1/2) of 132 min, or 36% (P < 0.025), and mean increase in metabolic clearance rate (MCR) of 148 l/day, or 42% (P < 0.001). Increase in the excretion of urinary radioactivity, predominantly in the conjugated fractions, was noted. Theophylline and placebo therapy resulted in no significant changes in dexamethasone t1/2 or MCR. The rate of urinary excretion of radioactivity was reduced after theophylline treatment. Since ephedrine accelerates labeled dexamethasone clearance while theophylline does not, caution is necessary when prescribing ephedrine for asthmatics requiring long-term therapy with dexamethasone and probably other corticosteroids. Theophylline appears to be a more appropriate bronchodilator for these patients.