THE ESTIMATION OF PHARMACOKINETIC PARAMETERS AND ACCURACY OF THE PREDICTED EQUATION FOR LITHIUM DOSE IN CHILDREN: A PILOT STUDY AT THE YUWAPRASART WAITHAYOPATHUM CHILD PSYCHIATRIC HOSPITAL

Objective: The purpose of the study was to estimate the pharmacokinetic parameters and calculate the precision (%RMSE) of the predicted lithium concentration equation.Methods: This research was studied from blood Lithium levels of Children who had visited Yuwaprasart Waithayopathum Child Psychiatric Hospital from 31 December 2009-1 January 2011 The accuracy and precision of the equation were evaluated by the mathematical principle. The assist package software (WIN-NONLIN) was used to create pharmacokinetic parameters.Results: Twenty-nine patients were recruited. The characteristics (mean+SD) presented as the following; age = 15.79+2.64 y, weight = 69.75+22.28 kg and the daily dose = 858.62+274.53 mg. The trough Lithium concentrations (mean+SD) = 0.56+19 mg/l. The kinetic parameter (Mean+SD) presented as the following; t1/2 =7.23+3.38 hr., ke =0.12+0.07 hr-1, Vd = 48.83+15.60 L, AUC0-12 =11.01+5.61 mg x hr/l. The population pharmacokinetic parameters; ke, and AUC (0-∞) = 0.151 hr-1 and 169.81, mg x hr./l respectively. The modified equation from Yukawa for lithium clearance calculation and prediction lithium concentrations were CL (mL/min) = [36.5+(0.242x BW (kg)-7.79]/Scr (mg/dL) and lithium concentration (mg/l) = 4 x Dose (mg)/CL (mL/min)x73.89, respectively with 6.39 %RMSE (test for 20 patients data).Conclusion: In conclusion, the modified Yukawa equation may be used for the prediction of lithium concentration with 6.39% RMSE