Urinary D-glucaric acid excretion and plasma antipyrine kinetics during enzyme induction.

1 Changes in urinary D-glucaric acid excretion following a 14 day course of antipyrine to produce enzyme induction have been compared in normal volunteers with changes in plasma half lives and steady state levels of antipyrine. 2 Urinary D-glucaric acid excretion for the group rose significantly with induction, while there was a significant fall in the mean plasma antipyrine half life and steady state levels. The extent of the increase in urinary D-glucaric acid excretion was inversely related to the pre-induction level, and this also applied to the change in antipyrine half lives. 3 Although in individuals, urinary D-glucaric acid excretion and plasma levels of antipyrine changed in parallel, there was no numerical correlation in the group as a whole between these two tests either before or after enzyme induction. 4 These findings are consistent with other recently reported evidence that plasma drug kinetics and other microsomal enzyme functions are not necessarily affected to the same degree by agents with enzyme inducing properties.