The effect of inducing drug therapy on the relationship between in vitro (cytochrome P-450 content) and in vivo (antipyrine kinetics) was investigated by comparing eleven consecutively treated epileptics with two groups of controls, eleven subjects with normal liver histology and eleven disease matched non-epileptics, all underwent diagnostice liver biopsy. 2. The epileptics had significantly higher cytochrom P-450 level in biopsies and they also metabolized antipyrine faster than the controls. 3. Decrease in antipyrine half-life in epileptics was related with alterations in liver histology, whereas the level of cytochrome P-450 was not. 4. There was a linear relationship between these two indices of enzyme induction when regressed on logarithmic data.
