Abstract: S-mephenytoin and debrisoquin hydroxylation abilities were investigated in 118 normal Chinese Zhuang minority volunteers after co-administration po 100 mg racemic mephenytoin(MP)and 10 mg debrisoquin (DB). The ratio between S-and R-enantiomers of mephenytoin in urinewas determined by implication of GC-NPD and used as the measure of the drug hydroxylation. 2 ofthe 118 subjects had S/R ratios greater than 1.0 and were poor hydroxylators of S- mephenytoin. The frequency of S-mephenytoin poor metabolizers (PM) was 10.2%. No PM of debrisoquin was found in the volunteers. It indicated that there was no relationship between S-mephenytoin P(4')-hydroxylation and debrisoquin 4-hydroxylation polymorphisms in Chinese Zhuang Minority population. In addition, 16 of the 118 volunteers(4 PMs and 12 EMs of S-mephenytoin) were se-lected to conduct the elimination kinetic studies of racemic mephenytoin and debrisoquin in urine. The pharmacokinetic parameters of S-, R- mephenytoin, DB and 4-OH-DB were calculated.

Key words: Mephenytoin, Debrisoquin, Hydroxylation, Inheritic polymorphism, Pharmacokinetics, Gas chromatography