Objective To study the effect of inhibitors of the multidrug transporters including P-glycoprotein (PGP)and multi-drug resistance-associated protein(MRP)on the regulation of concentration of oxcarbazepine in the extra-cellular fluid of the hippocampus after pilocarpine induced seizures in rats.To investigate whether oxcarbazepine are sub-strate for PGP and MRP and whether brain expressions of PGP and MRP are involved in muhidrug resistance mechanisms of refractory epilepsy.Methods The epileptic rats model were established by repeated peritoneal injection treatment with pi-locarpine.Thirty-two Wistar rats were divided into four groups:control group,pilocarpine epileptic model group,verapamil treated group and probenecid treated group.At 30,60,90,120 and 150 min following systemic injection of oxcarbazepine (80 mg/kg),dialysate was collected and the concentration of oxcarbazepine in the extracellular fluid of hippocampus was determined by microdialysis and high-performance liquid chromatography technique.Results After systemic injection of oxcarbazepine,the concentration of oxcarbazepine in extracellular fluid of the hippocampus during 90～150 min(1.26±0.09、0.93±0.10)were much higher in verapamil treated group than in pilocarpine epileptic model group(0.87±0.06、0.66±O.04)(P<0.05)and the concentration of oxcarbazepine in the hippocampus during 60～150 min(1.07 4±0.11、1.32±O.13、1.02±0.10、0.87±0.08)were higher in probenecid treated group than in pilocarpine epileptic model group (0.81±0.08、0.87±0.06、0.66.4±0.04、0.58±0.06)(P<0.05).Conclusions Oxcarbazepine are substrates for PGP and MRP and,penetration of oxcarbazepine through blood-brain barrier are restricted by PGP and MRP.Increased expres-sions of PGP and MRP in brain maybe involved in the mechanisms of multidrug resistance of refractory epilepsy.