OBJECTIVE: Routine clinical pharmacokinetic data collected from epileptic out-patients who received
phenytoin (PHT) were
analysed to estimate population pharmacokinetic parameters (PPK) using NONMEM program. METHODS : There were 361 steady-state serum PHT concentrations and associated dosage(mg· d-1) from 219 outpatients. RESULTS: The Vin and Km of PHT in a 60kg adult out-patients without combination with other drugs (phenobarbital, clonazepam or diazepam) were estimated to be 43 3 mg·d-1 and 5.84mg·mg-1 respectively. The best function adjusts Vm to the 0.56 power in proportion to body weight. The Km for patients less than 15 years old was 6% less than for adults. The Vm of patients treated with PHT combined with phenobarbital, clonazepam or diazepam will increase 7.7mg· d-1. Conclusion: Nonmen program could be used in
individual dosage of phenytoin. The mean
absolute error and mean absolute percent error of daily dosage, steady-state serum concentration between predicted and observed values were 13.54 ± 4.17 mg·d-1 and 5.31 ± 1.62%, 1.46 ± 0.82mg·L-1 and 10.22 ± 5.46% respectively in retrospective analysis of data of 219 out-patients. The mean absolute error and mean absolute percent error between observed and predicted PHT levels were 0.97 ± 0.31 mg· L-1 and 6.82 ± 2.12% in prospective analysis of 54 out-patients with one-point regression. CONCLUSION: Nonmen could be used in individual dosage of pheuytoin.