Abstracts

Rationale: Treatment of epilepsy often imposes an exposure to various anti-epileptic medications (AEDs) and requires long-term commitment and adherence from the patient. With the increasing number of AED choices since early 1990s, it can be challenging to decide which AED should be used for individual patients with epilepsy. Two main considerations in selecting AEDs are their efficacy and tolerability, which are probably best evaluated by retention rate, defined as the percentage of patients remaining on the medication after a specified time period. We examined the retention rate of clobazem (CLB) and compared to the previously published retention rate of other AEDs. Methods: Retention data of CLB was obtained retrospectively by reviewing medical records from the epilepsy center at the Barrow Neurological Institute and interviewing patients if necessary. The data collection included patient's age, gender, seizure type, concurrent AEDs, CLB dosages, overall CLB seizure outcome, adverse effects, main reasons for discontinuation if discontinued, and duration of therapy. Patients who started CLB during pivotal clinical studies were excluded, and only the patients who started CLB after being commercially available on October 24, 2011 were included in the study. In addition, in order to access longer retention rate, patients were excluded if CLB was initiated after December 2013. Results: A total of 81 patients (56% male) started CLB therapy prior to 2014 for medically refractory epilepsy. 30% of patients had Lennox-Gastaut syndrome and remaining had partial onset or unclear types. CLB was initiated as an adjunctive therapy in all patients. The overall one year retention rate of CLB was 81.5% (66 of 81), and among those people who started CLB more than two years ago, the two year retention rate was 75.7% . Interim retention rates at 3 month were 95.1%, and at 6 months, 85.2%. When compare to other AED retention rates in 12 months from the same clinic, CLB retention was better than levetiracetam (57%), oxcarbazepine (61%), topiramate (45%), or zonisamide (61%), but similar to lamotrigine (75%) or lacosamide (76%). When CLB was discontinued, it was mainly due to agitation or irritability (30%), inefficacy (30%), financial reasons (15%), and sedation (10%). Other reasons (<10%) of stopping CLB were insomnia, dizziness, or GI discomfort. In terms of efficacy, the reported 50% responder rates were 59.0% during the study period. Conclusions: Comparing retention rates of AEDs may provide useful insight into their tolerability and efficacy in epilepsy treatment. This study shows high retention rate of CLB at 12 months when compare to other newer AEDs at the same time frame. Beside ineffectiveness, leading causes of CLB discontinuation were agitation or irritability and sedation. In addition, CLB provided meaningful seizure control for many patients with refractory epilepsy.