Furosemide potentiates the anticonvulsant action of valproate in the mouse maximal electroshock seizure model

Accumulating evidence indicates that furosemide (FUR, a loop diuretic) exerts the anticonvulsant action in various in vitro and in vivo experiments. Therefore, the aim of this study was to assess the influence of FUR on the protective action of numerous conventional and newer antiepileptic drugs (carbamazepine [CBZ], lamotrigine [LTG], oxcarbazepine [OXC], phenobarbital [PB], topiramate [TPM] and valproate [VPA]) in the mouse maximal electroshock seizure (MES) model. Results indicate that FUR (up to 100mg/kg, i.p., 30min before the test) neither altered the threshold for electroconvulsions nor protected the animals against MES-induced seizures in mice. FUR (100mg/kg, i.p.) enhanced the anticonvulsant effects of VPA in the MES test by reducing its ED50 value from 230.4 to 185.4mg/kg (P<0.05). In contrast, FUR at 100mg/kg had no significant effect on the antielectroshock action of the remaining drugs tested (CBZ, LTG, OXC, PB, and TPM) in mice. Estimation of free plasma and total brain VPA concentrations revealed that the observed interaction between FUR and VPA in the MES test was pharmacodynamic in nature because neither free plasma nor total brain VPA concentrations were altered after i.p. administration of FUR. In conclusion, one can ascertain that the selective potentiation of the antielectroshock action of VPA by FUR and lack of any pharmacokinetic interactions between drugs, make this combination of pivotal importance for epileptic patients treated with VPA and received FUR from other than epilepsy reasons.