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The effective and safe use of phenytoin in epileptic patients is complicated by its nonlinear pharmacokinetic characteristic, Michaelis-Menten type which is reported by numerous investigator. Currently, Bayesian method which estimates the most probable parameters of V max and Km of the drug for each patient from population parameters data is very useful approach for adjusting phenytoin dosage. The pharmacokinetic parameters of phenytoin are affected by physiological factor, disease state, compliance, bioavailability and ethnic origin. To increase the accuracy of Bayesian method, it is desirable to use population parameters of Korean. Therefore, in the present study, pharmacokinetic parameters of phenytoin have been compared between Caucasian and Korean. Data from 20 adult neurology outpatients having normal liver and renal function from Seoul National University Hospital and University of Minnesota Hospital respectively were evaluated. Phenytoin pharmacokinetic parameters, Vmax & Km, were obtained from these two dose-concentration data at each steady-state by using Michaelis-Menten equation. Estimated mean values of Vmax and Km were 6.72㎎/㎏/day(SD 1.34 : CV 20%) and 4.77mcg/㎖(SD 2.39 : CV 50%), respectively in Korean. The corresponding values were 8.39㎎/㎏/day(SD 2.29 : CV 27%) and 6.67mcg/㎖(SD 6.04 : CV 90%) from Caucasian. Vmax were significantly different between two groups(p<0.05)
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