Abstracts

RATIONALE: We have previously reported the combination of valproate and lamotrigine to be highly effective as measured by improved seizure control after initiation of the therapeutic regimen. This study applies intent to treat methodology to validate our previous observations. METHODS: All 41 adult and pediatric patients, ages 7-63 (mean = 38.2), with partial seizures who were initiated on valproate and lamotrigine combination therapy at Minnesota Epilepsy Group Clinic between September 1994 and January 2000 were included in the study. On average, these patients failed 2.9 medications (range 1-5) prior to initiation. For purposes of this study, no other antiepileptic medications were administered while these patients were on valproate and lamotrigine combination therapy. Average length on valproate/lamotrigine therapy lasted 63.8 weeks (range 12-285). Mean blood level for valproate was 63.0 mcg/ml; mean blood level for lamotrigine was 12.7 mcg/ml. Mean dosages of valproate and lamotrigine were 990.9 mg/day and 321.9 mg/day, respectively. RESULTS: Fourteen patients (34.1%) were seizure free as a result of the medication regimen. An additional 13 patients (31.7%), although not seizure free, had a seizure reduction of 50% or greater. Combined, 27 patients (65.8%) had a seizure reduction of 50% or greater. Of these 41 patients, 29 successfully remained on the valproate/lamotrigine therapy. For these 29 patients, seizure frequency was reduced from an average of 10.3 seizures per month to an average of 1.6 seizures per month (p<.05). Three of the 41 patients had side effects necessitating discontinuation (ataxia, double vision, tremors, and/or shakiness). None had a rash. Nine of the 41 patients discontinued due to lack of perceived efficacy. CONCLUSIONS: Valproate and lamotrigine in combination therapy effected a significant reduction in seizures, including 34.1% seizure free and, overall, 65.8% with a seizure reduction of 50% or greater. It is, therefore, a highly effective combination therapy.