Objective: To investigate interaction between orally given Centella asiaticaûs ethyl acetate fraction (EACA) and intraperitoneally administered antiepileptic drugs (AEDs), namely, phenytoin, valproate and gabapentin.
Material and Method: Isobolographic analysis was used to evaluate the interaction between EACA and AEDs in terms of protection of mice in the pentylenetetrazole test. Rotarod test was used to evaluate neurotoxicity.
Results: When given alone, the median effective dose of phenytoin, valproate and gabapentin were found to be 13, 104, and 310 mg/kg BW, respectively, whereas the corresponding values in the presence of EACA were 5, 29 and 79 mg/kg BW. Together with isobolographic analysis, the results obtained indicated an additive effect among all combinations tested. In relation to neurotoxicity, combination of gabapentin and EACA demonstrated a broader margin between the effective dose and the neurotoxic dose while the other two combinations did not.
Conclusion: The present finding suggested a potential of Centella asiatica to be developed as an adjunctive medication for epileptic patients.

Keywords: Centella asiatica, Anticonvulsant activity, Isobologram