MONITORING FREE EXTRACELLULAR VALPROIC ACID BY MICRODIALYSIS IN EPILEPTIC PATIENTS

This report describes the first experiences with monitoring of valproi c acid pharmacokinetics in patients with epilepsy by subcutaneous micr odialysis. We could demonstrate good correspondence between total conc entration in plasma and free concentration in plasma and dialysate. In this study the dialysate concentrations were not corrected for in viv o recovery because the aim was to explore the possibilities of the met hod in routine clinical work rather than to estimate absolute concentr ations in extracellular fluid. In one patient, microdialysis was conti nued for 3 days without problems. The dialysis probe with a small port able pump could be carried without any notable interference with daily activities of patients in the ward. No side effects were noted. The r esults encourage further studies along two lines: to investigate the f ree-concentration effect relation for valproic acid and to monitor dru g concentration under nonhospital conditions in order to study the int eraction between daily activities and drug concentration.