The aim of this study was to determine the effects of 4-(4-bromophenyl)-5-(3-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazole-3-thione (TP4-a new S-triazole derivative possessing anticonvulsant properties in preclinical studies) on the protective action of four different classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) against maximal electroshock-induced seizures in mice. Results indicate that TP4 administered intraperitoneally at doses of 75 and 100 mg/kg significantly elevated the threshold for electroconvulsions in mice. TP4 at doses of 12.5, 25, 37.5 and 50 mg/kg had no impact on the threshold for electroconvulsions in mice. Moreover, TP4 (50 mg/kg) significantly enhanced the anticonvulsant activity of carbamazepine, phenobarbital and valproate, but not that of phenytoin in the maximal electroshock seizure test in mice. TP4 at 25 mg/kg significantly potentiated the anticonvulsant action of carbamazepine, but not that of phenobarbital, phenytoin and valproate in the mouse maximal electroshock-induced seizure model. Pharmacokinetic experiments revealed that TP4 significantly elevated total brain concentrations of carbamazepine and valproate, having no impact on total brain concentrations of phenobarbital in mice. In conclusion, the enhanced anticonvulsant action of phenobarbital by TP4 was probably pharmacodynamic in nature and, therefore, the combination of TP4 with phenobarbital is worthy of consideration while extrapolating the results from this study into clinical settings. The enhanced anticonvulsant action of carbamazepine and valproate by TP4 in the mouse maximal electroshock-induced seizure model was associated with pharmacokinetic increases in total brain concentrations of the antiepileptic drugs in mice. The combination of TP4 with phenytoin was neutral from a preclinical point of view.
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