AUTOMATED-ANALYSIS OF FREE AND TOTAL CONCENTRATIONS OF 3 ANTIEPILEPTIC DRUGS IN PLASMA WITH ONLINE DIALYSIS AND HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A fully automated method for determination of the free and total conce ntration of drugs with a varying degree of protein binding is describe d. The antiepileptic drugs phenytoin, carbamazepine and phenobarbitone were chosen to demonstrate the utility of this technique. The method was based on the ASTED system and combined on-line equilibrium dialysi s at 37 degrees C with concentration of the dialysate on a trace enric hment column and HPLC determination with UV detection. The dialysis ce ll was a modification of the ASTED dialysis cell and 22% of the free c oncentration of the drugs were recovered in the recipient channel of t he dialyser after 10 min of dialysis at 37 degrees C. The free concent ration, the total concentration as well as the drugs protein binding c ould be determined. The method was shown to be well suited for routine monitoring of the free and the total concentrations of the drugs in p lasma from epileptic patients.