text: Abstract 1. We investigated the effects of the dose of and the number of times an inducer was administered and the duration of induction of hepatic and intestinal << cytochrome P450 3A >> (CYP3A) in rats using dexamethasone 21-phosphate ([[ DEX-P ]]) and midazolam (MDZ) as an inducer and a substrate to CYP3A, respectively.