Interactions of levetiracetam with ethosuximide in the mouse 6 Hz psychomotor seizure model - a type II isobolographic analysis

The aim of the present study was to characterize the anticonvulsant effects of levetiracetam in combination with ethosuximide in the mouse 6 Hz psychomotor seizure model. Limbic (psychomotor) seizure activity was evoked in albino Swiss mice by a current (32 mA, 6 Hz, 3 s stimulus duration) delivered via ocular electrodes; type II isobolographic analysis was used to characterize the consequent anticonvulsant interactions between the drug combinations for fixed-ratios of 1:1, 1:2, 1:5 and 1:10. With type II isobolographic analysis, the combinations of levetiracetam with ethosuximide for the fixed-ratios of 1:5 and 1:10 were supra-additive (synergistic; P<0.05 and P<0.01, respectively) in terms of seizure suppression, while the combinations for the fixed-ratios of 1:1 and 1:2 were additive in the mouse 6 Hz psychomotor seizure model. The combinations of levetiracetam with ethosuximide for the fixed-ratios of 1:5 and 1:10 appear to be particularly favorable combinations exerting supra-additive interaction in the mouse 6 Hz psychomotor seizure model. Finally, it may be concluded that because of the synergistic interactions between levetiracetam and ethosuximide, the combination might be useful in clinical practice.