Influence of aminophylline on the anticonvulsive action of gabapentin in the mouse maximal electroshock seizure threshold model

Accumulating evidence indicates that aminophylline [theophylline(2) center dot ethylenediamine] markedly attenuates the anticonvulsant action of conventional antiepileptic drugs in experimental animal models of epilepsy and evokes severe seizure activity in patients treated with this methylxanthine. The objective of this study was to determine the influence of acute (single) and chronic (twice daily for 14 consecutive days) treatments with aminophylline on the anticonvulsant potential of gabapentin (a second-generation antiepileptic drug) in the mouse maximal electroshock seizure threshold model. Additionally, the effects of acute and chronic administration of aminophylline on the adverse effect potential of gabapentin in terms of motor coordination impairment were assessed in the chimney test. To evaluate pharmacokinetic characteristics of interaction between drugs, total brain concentrations of gabapentin and theophylline were estimated with high-pressure liquid chromatography and fluorescence polarization immunoassay, respectively. Results indicated that gabapentin (at doses of 75 and 100 mg/kg, i.p.) increased the threshold for electroconvulsions in mice. Aminophylline in non-convulsive doses of 50 and 100 mg/kg (i.p.), both in acute and chronic experiments, did not attenuate the anticonvulsant potential of gabapentin in the maximal electroshock seizure threshold test in mice. Similarly, aminophylline at a dose of 100 mg/kg had no impact on the adverse effect potential of gabapentin in the chimney test. Pharmacokinetic evaluation of total brain concentrations of gabapentin and theophylline revealed no significant changes in total brain concentrations of the drugs after both, acute and chronic applications of aminophylline in combination with gabapentin. The data show that aminophylline did not alter the ability of gabapentin to protect mice against seizures induced by electroconvulsive shock. The observed interaction between gabapentin and aminophylline in both acute and chronic experiments was pharmacodynamic in nature.