RESUMO
Rufinamide is a third-generation antiepileptic drug, approved recently as an orphan drug for the treatment of Lennox-Gastaut syndrome. Although extensive research was conducted, its pharmacokinetics in rats was not described. This work addresses that area by describing in a rapid pharmacokinetic study the main pharmacokinetic properties of rufinamide at three different doses of 1 mg/kg body weight (bw), 5 mg/kg bw, and 20 mg/kg bw. Furthermore, total brain concentrations of the drug were determined in order to characterize its brain-to-plasma partition coefficient. Adult Wistar male rats, weighing 200-450 g, were administered rufinamide by intravenous and oral routes. Rufinamide concentrations from plasma samples and brain tissue homogenate were determined using a liquid chromatography-mass spectrometric method and pharmacokinetic parameters were calculated. The mean half-life was between 7 and 13 h, depending on route of administration--intravenously administered drug was eliminated faster than orally administered drug. Mean (S.E.M.) total plasma clearance was 84.01 ± 3.80 ml/h/kg for intravenous administration, while the apparent plasma clearance for oral administration was 95.52 ± 39.45 ml/h/kg. The mean (S.E.M.) maximum plasma concentration reached after oral administration of 1 mg/kg bw and 5 mg/kg bw was 0.89 ± 0.09 µg/ml and 3.188 ± 0.71 µg/ml, respectively. The median (range) time to reach maximum plasma concentration (t(max)) was 4 (2-8)h. Mean (S.E.M.) brain-to-plasma concentration ratio of rufinamide was 0.514 ± 0.036, consistent with the brain-to-plasma ratio calculated from the area under curves (AUC(0-t)) of 0.441 ± 0.047. No influence of dose, route of administration, or post-dosing time was observed on brain-to-plasma ratio.
