PT  - JOURNAL ARTICLE
AU  - Ralph Clinckers
AU  - Ilse Smolders
AU  - Alfred Meurs
AU  - Guy Ebinger
AU  - Yvette Michotte
TI  - Quantitative in Vivo Microdialysis Study on the Influence of Multidrug Transporters on the Blood-Brain Barrier Passage of Oxcarbazepine: Concomitant Use of Hippocampal Monoamines as Pharmacodynamic Markers for the Anticonvulsant Activity
AID  - 10.1124/jpet.105.085514
DP  - 2005 Aug 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 725--731
VI  - 314
IP  - 2
4099  - http://jpet.aspetjournals.org/content/314/2/725.short
4100  - http://jpet.aspetjournals.org/content/314/2/725.full
SO  - J Pharmacol Exp Ther2005 Aug 01; 314
AB  - Various antiepileptic drugs were shown to be substrates for multidrug transporters at the level of the blood-brain barrier. These ATP-dependent efflux pumps actively limit brain accumulation of xenobiotics and drugs. Intrahippocampal oxcarbazepine perfusion in rat was previously shown to exert anticonvulsant effects associated with increases in extracellular dopamine and serotonin levels. In contrast, preliminary studies in our laboratory revealed that no anticonvulsant or monoaminergic effects could be obtained after systemic oxcarbazepine administration. The present in vivo microdialysis study was conducted to investigate the impact of the transport kinetics of oxcarbazepine across the blood-brain barrier on the observed treatment refractoriness. More precisely, the influence of intrahippocampal perfusion of verapamil, a P-glycoprotein inhibitor, and probenecid, a multidrug resistance protein inhibitor, on the blood-brain barrier passage and anticonvulsant properties of oxcarbazepine were investigated in the focal pilocarpine model for limbic seizures. Simultaneously, the effects on hippocampal monoamines were studied as pharmacodynamic markers for the anticonvulsant activity. Although systemic oxcarbazepine administration alone failed in preventing the animals from developing seizures, coadministration with verapamil or probenecid offered complete protection. Concomitantly, significant increases in extracellular hippocampal dopamine and serotonin levels were observed within our previously defined anticonvulsant monoamine range. The present data indicate that oxcarbazepine is a substrate for multidrug transporters at the blood-brain barrier. Coadministration with multidrug transporter inhibitors significantly potentiates the anticonvulsant activity of oxcarbazepine and offers opportunities for treatment of pharmacoresistant epilepsy. The American Society for Pharmacology and Experimental Therapeutics