6 beta-Hydroxycortisol: a noninvasive indicator of enzyme induction.

We measured urinary 6 beta-hydroxycortisol (6 beta OHF) excretion in normal children and in children receiving anticonvulsant therapy with phenobarbital or diphenylhydantoin, 6 beta OHF excretion increased 4- to 7-fold during anticonvulsant therapy. The marked increase in the ratios of 5 beta OHF to 17-hydroxycorticosteroid and 6 beta OHF to free cortisol suggests that the measured increase in urinary 6 beta OHF may serve as an index of induction of the microsomal mixed function oxidase system. This noninvasive approach allows rapid assessment of the effects of drugs and foreign compounds on microsomal hydroxylation of cortisol. This convenient probe can be applied, with particular ease, to further studies in children in whom characterization of the effects of drugs and xenobiotic compounds on hepatic hydroxylation is of interest.