Interference in the Effect of Dexamethasone by Diphenylhydantoin

Abstract

INTERACTION between drugs is recognized, currently, as a serious problem in clinical medicine. High on the list of possibilities are interferences between steroid hormonal compounds and various drugs because of the known similarities in their metabolism.1 We first became aware of an inhibitory effect of diphenylhydantoin (DPH) on the action of dexamethasone several years ago during studies in which DPH was evaluated therapeutically for Cushing's syndrome.2 Initially, the interaction was considered unique in this condition, and subsequent observations in other patients demonstrated only a slight interference in the excretion of urinary 17-hydroxycorticosteroids (17-OHCS) during standard dexamethasone suppression tests. More recently, . . .