Efficacy and safety of gabapentin as an add-on therapy in refractory partial epileptic patients

The study on the efficacy and safety of gabapentin as an add-on therapy trial was performed in 10 refractory partial seizure cases at Prasat Neurological Institute, Thailand from September 1996 to July 1998. This was an open-labeled titration dose of gabapentin starting at 600 mg/day add-on to the previously prescribed conventional antiepileptic drugs (AEDs). In cases that seizures could not be controlled, gabapentin dose was increased by 300 mg per day every two weeks until the total dose of 3,000 mg or until the side effects became intolerable. The result revealed that gabapentin reduced frequency, duration and severity of seizures and also improved the patients' activities of daily living (ADL) even at the minimum dose of 600 mg. The optimal dose of gabapentin was in the range of 600 to 1,200 mg per day. Seven patients were seizure free at the end of the study. There were some precipitating factors that interfered with the efficacy of gabapentin in some patients such as stress, menstruation, fever, and alcohol intake. Weight gain, somnolence, nystagmus, and dizziness were the major adverse events in these patients, whereas ataxia, tremor, and diplopia were found with gabapentin in a dose higher than 1,800 mg/day. These adverse events were mild and transient. No patients withdrew from the study due to adverse drug reactions. In addition, gabapentin did not alter conventional AED blood level and routine laboratory parameters. In conclusion, gabapentin was effective and well tolerated as an add-on therapy in refractory partial epileptic Thai patients.