ИСТИНА

Introduction: Carbamazepine (CBZ) is a first-line antiepileptic drug; however, >25% patients are resistant to CBZ. Although the mechanism of resistance to CBZ is not totally clear, some facts are pointing to the role of the P-glycoprotein (Pgp), the ABC transporter expressed by the brain endothelium [1]. As shown by our previous studies, the PLGA nanoparticles coated with poloxamer 188 (PLGA/P188 NPs) enhance delivery of the Pgp substrates across the blood-brain barrier (BBB) [2]. Therefore, the objective of the present study was to investigate the possibility to enhance the anticonvulsive effect of CBZ using the PLGA/P188 NPs as a brain delivery system Methods: CBZ-loaded PLGA NPs were prepared by a homogenization solvent evaporation technique. The CBZ:PLGA ratio was 1:10 (w/w). Before injection, the freeze-dried NPs were resuspended in a 1% solution of poloxamer 188 (P188) or water for injections and incubated for 30 min. The average particle size was 130-150 nm (PDI 0.16-0.17). The drug encapsulation efficiency was calculated as the ratio between the unloaded drug and the total drug concentration and was found to be 80%. Seizures were induced in male Wistar rats by i.p. administration of isoniazid (ISN, 300 mg/kg).Treatment. CBZ, free or bound to PLGA/P188 NPs, was injected i.v. 45 min before ISN (n = 10). Additionally, for evaluation of the CBZ interaction with the Pgp, some animals were pretreated with verapamil (Ver+CBZ, Ver+CBZ-NP), a Pgp inhibitor (40 mg/kg i.p 60 min before CBZ formulations). The pharmacological effect was evaluated by duration, intensity, and latency of the ISN-induced seizures Results: Binding of CBZ to PLGA/P188 NPs dramatically enhanced its anticonvulsive effect against ISN-induced seizures: duration of the seizures and their intensity (Racine scale) were decreased, and latent period was prolonged. In particular, after injection of 1 mg/kg of CBZ-NP the seizure intensity was decreased to stage 1, whereas with free CBZ a similar effect could be achieved only after the dose of 30 mg/kg. Interestingly, whereas pretreatment with verapamil considerably enhanced the efficacy of free CBZ, it produced no effect on the CBZ-NP action. Similar phenomena were observed for seizures duration and latencies (not shown). Conclusion: Anticonvulsive effect of CBZ was considerably enhanced by binding the drug to the P188-coated PLGA nanoparticles. This phenomenon could be attributed to the enhanced brain delivery of CBZ by nanoparticles. Enhancement of the CBZ effect by verapamil confirms that CBZ is a Pgp substrate, whereas the fact that verapamil did not exert any influence on the CBZ-NP may suggest that the mechanism of the nanoparticle transport across the BBB is not related to the Pgp.