Pluronic P85 decreases the delivery of phenytoin to the brain in drug-resistant rats with P-glycoprotein overexpressed chronic mesial temporal lobe epilepsy.

P-glycoprotein (Pgp) overexpressed in blood brain barrier (BBB) is hypothesized to lower brain drug concentrations and thus inhibit anticonvulsant effects in drug-resistant epilepsy. Pluronic P85 (P85) was proved to enhance the delivery of drugs into the brain by inhibition of Pgp. To determine whether the surfactant P85 [versus Pgp inhibitor tariquidar (TQD)] enhance phenytoin (PHT) into the brain in drug-resistant rats with chronic mesial temporal lobe epilepsy (MTLE) induced by lithium-pilocarpine, in brain of which Pgp were overexpressed, then direct verification of PHT transport via measurement of PHT concentration in brain using microdialysis. The drug-resistant model rats were randomly divided into three groups, which were treated with PHT, 1%P85 + PHT, or PHT+TQD, respectively. 1%P85 + PHT treatment displayed a lower ratio of the area under the curve (AUC) of the PHT concentration in the brain/plasma even than that of the PHT treatment in model rats (p < 0.05), while PHT+TQD showed the highest ratio of the AUC of all treatments. However, the ratio of the PHT concentration in the liver/plasma was similar in three model groups (p > 0.05). For the ratio of the kidney/plasma, PHT+TQD treatment model group had the highest ratio of the other treatments in model rats. Thus, P85 oppositely decreased PHT concentration in brain in drug-resistant model rats with Pgp overexpressed MTLE while TQD could increase PHT distribution in brain.