title: Antiepileptic drugs modulate P-glycoproteins in the brain: a mice study with (11)C-desmethylloperamide.
abstract: P-glycoprotein transporters (P-gp) located at the blood-brain barrier (BBB) are likely to play a role in refractory epilepsy. In vitro studies already pointed out that several antiepileptic drugs (AEDs) are substrate of P-gp. This study proposes a new in vivo approach to investigate the interaction between some AEDs and P-gp located at the BBB. (11)C-desmethylloperamide ((11)C-dLop), a radiolabelled substrate of P-gp, was intravenously administrated after pretreatment with saline or AEDs (sodium valproate, levetiracetam, topiramate and phenytoin) at their human therapeutic and four times their therapeutic dose. The effect of the different pretreatment on the intracerebral concentration of (11)C-dLop was determined to indirectly investigate possible in vivo interactions between AEDs and P-gp. Pretreatment with levetiracetam, topiramate and phenytoin at therapeutic doses significantly decreased intracerebral concentration of (11)C-dLop. Pretreatment with a therapeutic dose of sodium valproate did not influence brain uptake of (11)C-dLop. In case of pretreatment with supratherapeutic doses of AED, (11)C-dLop brain uptake was not different compared to pretreatment with saline. The metabolisation rate of (11)C-dLop in plasma was unaltered, indicating that observed differences in brain uptake of the tracer were not due to pharmacokinetic changes. The following conclusion can be made: levetiracetam, topiramate and phenytoin demonstrate biphasic modulation of the BBB P-gp. At therapeutic doses they act as inducers of efflux, at supratherapeutic doses they have no effect on the efflux rate. Sodium valproate does not interact with P-gp at therapeutic nor at higher doses.
authors.affiliation: Laboratory of Radiopharmacy, Ghent University, Harelbekestraat 72, B-9000 Ghent, Belgium. Lieselotte.Moerman@Ugent.be
authors.forename: Lieselotte
authors.initials: L
authors.lastname: Moerman
authors.forename: Leonie
authors.initials: L
authors.lastname: Wyffels
authors.forename: Dominique
authors.initials: D
authors.lastname: Slaets
authors.forename: Robrecht
authors.initials: R
authors.lastname: Raedt
authors.forename: Paul
authors.initials: P
authors.lastname: Boon
authors.forename: Filip
authors.initials: F
authors.lastname: De Vos
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000172:deficiency / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D000927:Anticonvulsants / Q000097:blood / Q000494:pharmacology*; D001812:Blood-Brain Barrier / Q000187:drug effects / Q000378:metabolism; D001921:Brain / Q000000981:diagnostic imaging* / Q000187:drug effects*; D002247:Carbon Isotopes / Q000097:blood / Q000378:metabolism* / Q000493:pharmacokinetics; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D008139:Loperamide / Q000031:analogs & derivatives* / Q000097:blood / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D011869:Radioligand Assay; D011877:Radionuclide Imaging; D013997:Time Factors
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000927:Anticonvulsants; D002247:Carbon Isotopes; C419149:N-demethylloperamide; D008139:Loperamide; C095122:multidrug resistance protein 3