Additive interactions between retigabine and oxcarbazepine in the chimney test and the model of generalized tonic-clonic seizures in mice

Summary Introduction Patients with pharmacoresistant epilepsy are usually treated with two or more antiepileptic drugs (AEDs). The search for therapeutically efficacious AED combinations is still a challenging issue for clinicians and epileptologists throughout the world. Aim To determine the interaction profile for the combination of retigabine (RTG) and oxcarbazepine (OXC) in both, the model of tonic-clonic seizures, the maximal electroshock (MES)-induced seizure model and chimney test (motor performance) in adult male albino Swiss mice. Methods Isobolographic analysis (type I) was applied to characterize interactions for the combination of RTG with OXC with respect to its anticonvulsant and acute side (neurotoxic) effects, as determined in the MES and chimney tests, respectively. Results The combination of RTG with OXC at the fixed-ratios of 1:3, 1:1 and 3:1 produced additive interactions in the MES test in mice. Similarly, the combination of RTG with OXC at the fixed-ratio of 1:1 produced additive interaction with a tendency towards sub-additivity in the chimney test in mice. Measurement of total brain concentrations of both AEDs revealed that RTG did not affect total brain concentrations of OXC and inversely, OXC had no impact on RTG’s total brain concentrations, confirming pharmacodynamic interaction between the drugs. Conclusions The additive pharmacodynamic interactions in both the MES and chimney tests in mice were observed for the combination of RTG with OXC.