Abstracts

Rationale: Treatment of epilepsy often imposes an exposure to various anti-epileptic medications (AEDs) and requires long-term commitment and compliance from the patient. With the advent of the newer generation of AEDs starting in the early 1990s, neurologists have gained a number of new AEDs to choose from. 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 reviewed retention rate of newly approved AED, lacosamide (LCM), and compared to the previously published retention rate of other AEDs. Methods: Retention data of LCM was obtained retrospectively by reviewing medical records in our epilepsy center at the Barrow Neurological Institute and interviewing patients if necessary. The data included patient s age, gender, seizure type, current and previous medications, dosage, main reasons for discontinuation, and duration of therapy. To avoid as much recall bias as possible, we also reviewed electronic records, as well as previous dictations to make sure that obtained data are credible and accurate. Patients who started LCM during phase II and III clinical trials were excluded, and patients who started LCM after being commercially available on June 3, 2009 were included in the study. In addition, patients were excluded if LCM was recently initiated within six months or less in order to access longer retention rates. Results: Out of the total of 185 LCM exposures since June 3, 2009, 121 patients (53% female) were started LCM 6 months or longer for partial epilepsy treatment. LCM was initiated as an adjunctive therapy in all 121 patients. The overall retention rate of LCM was 79.34% (96 of 121) in six months. The interim retention rate at one month was 94.21%, and at three months, 85.95%. When compare to other AED retention rates in 6 months from the same clinic, LCM retention was better than levetiracetam (62.2%), oxcarbazepine (68.0%), topiramate (56.4%), or zonisamide (65.6%), but similar to that of lamotrigine (78.5%). When LCM was discontinued, it was mainly due to inefficacy (36%), dizziness (28%), and lethargy (24%) within 6 months of LCM therapy. Other reasons (<10%) of stopping LCM were due to diplopia (8%), irritability (8%), headaches (8%), financial limitations (8%), rash (4%), nausea (4%), weight gain (4%), and unknown reasons (4%). 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 LCM at 6 months when compare to other newer AEDs at the same time frame. Beside ineffectiveness, leading causes of LCM discontinuation were dizziness and lethargy, although the overall incidence of these adverse effects was low (5.8% and 4.9% respectively).