Comparative Clinical Trial of Gabapentin and Sodium Valproate as Add-on Therapy in Refractory Partial Epilepsies: Open Randomized Multicenter Trial

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Abstract

PURPOSE: To compare the efficacy and safety of gabapentin (GBP) with sodium valproate (VPA) as add-on therapy in medically refractory partial epilepsies. METHOD: This was an open randomized multicenter trial. The study protocol consisted of 12 weeks of baseline phase, variable period of dose titration phase, and 12 weeks of maintenance phase. During baseline phase, the patient should have at least one seizure every 4 week period and six or more seizures during 12 week period. During dose titration phase, GBP was started with 300 mg/day for 4 days, then increased to 600 mg/day for 3 days, and then 900 mg/day for 7 days. From third week, GBP was increased by 600 mg/day every week to reach to the maximal dose of 5400 mg/day. VPA was increased by 300 mg/day every week up to the maximal dose of 3000 mg/day.
RESULTS
A total of 126 patients were randomized into GBP group (70 patients) and VPA group (56 patients). Twenty six patients were withdrawn from the study earlier and 100 patients (GBP : 57 patients, VPA : 43 patients) finished the study as planned. Baseline characteristics were not different between the groups. Intent-to-treat analysis (ITTA) of efficacies revealed that the median seizure frequency reduction rates were 52.5% for GBP and 49.7% for VPA, responder rates were 44% for GBP and 52% for VPA, and seizure free rate were 12% for GBP and 16% and VPA. These results were not statistically different. The efficacies on different types of seizure were also similar between the two drugs but simple partial motor seizure (SPMS), in which GBP was better than VPA (p=0.02). The incidence of adverse events and drop-out rate due to adverse events were also comparable.
CONCLUSION
GBP and VPA were equally effective and safe as add-on therapy in medically refractory partial epilepsies except SPMS which responded better to GBP.