Abstracts

Rationale: Using lacosamide, a novel, non-traditional sodium channel blocking AED, as add-on therapy in patients with partial-onset epilepsy has resulted in various treatment-emergent adverse events. We undertook this study to evaluate the tolerability of lacosamide in patients that were concomitantly either on at least one traditional sodium channel blocking AED or on AEDs that act on non-sodium channel targets. Methods: Retrospective chart review of 34 consecutive patients undergoing add-on therapy of lacosamide of up 400mg/day for intractable partial seizures. We collected data on concomitant AEDs classified as either non-sodium channel (NSCB) or sodium channel (SCB) blocking and compared number and character (e.g. dizziness, headache, nausea and vomiting, fatigue) of adverse events; necessary adjustments to concomitant AEDs or lacosamide; and number of discontinuations of lacosamide either due to intolerable adverse events or lack of efficacy between the two groups. Data were analyzed using Chi-square or t-test statistics, as appropriate. Results: At baseline, eight patients were on AEDs acting on non-sodium channel targets (e.g. valproate, levetiracetam, topiramate, zonisamide, pregabalin, phenobarbiatal, clonazepam). Twenty-six patients were on traditional sodium channel blocking AEDs (e.g. carbamazepine, lamotrigine, oxcarbazepine, phenytoin). The two groups were not significantly different in age (NSCB=33.3 ( /-14.6); SCB=33.9 ( /-14.1), p=0.9) nor gender distribution (p=0.4). There were no significant group differences in the number or character of adverse events to lacosamide (both p's>0.2). Neither the need to adjust concomitant AEDs (p=0.7) nor the percentage in reduction required (p=0.8) varied for the two groups. There were no differences between the groups as to who had to discontinue lacosamide either because of side effects of increase in seizures (p=0.2). Conclusions: Our study failed to show any difference in tolerability of lacosamide when added on to either a non-sodium channel blocking or traditional sodium channel blocking anticonvulsant agent. For our patients difficulties with tolerating lacosamide were not related to sodium channel classification of concomitant anticonvulsant medications. Indeed, patients on either type of concomitant medications experienced multiple adverse events. The reason for this difficulty with tolerability needs further evaluation.