Pedigree analysis of a subject with abnormally slow renal elimination of 6-hydroxychlorzoxazone.

The family of an unusual subject was studied. When tested with chlorzoxazone (CX; 250 mg p.o.) on four separate occasions 5 years ago, this subject showed abnormally slow renal elimination of 6-hydroxychlorzoxazone (HCX), the primary CX metabolite. Since rates of CX biotransformation to HCX have served as a probe of the important cytochrome P450 isozyme, CYP 2E1, it was of interest that this unusual subject had normal conversion of CX to HCX. The present study revealed that over the past 5 years this subject accelerated his renal rate of HCX elimination which now lies at the slow end of the curve for normal subjects. His wife and 5 children all had more rapid rates than he for renal HCX elimination.