Abstracts

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. Despite the wide selections, it is often unclear as to which AED should be used in a particular patient and efficacy or side effects alone do not adequately address the main question [ndash] will a patient stay on a drug through the years? Successful treatment consists of finding the balance between obtaining adequate seizure control and avoiding adverse effects; this is probably best measured and examined through retention rates, defined as the percentage of patients remaining on the medication after a specified time period. Retention data on commonly used newer AEDs (lamotrigine, levetiracetam, oxcarbazepine, topiramate, and zonisamide) were obtained retrospectively by reviewing medical records in our epilepsy center and interviewing patients if needed. The data included patient[apos]s age, gender, seizure type, current and previous medications, dosage, main reason 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 as much data as possible is credible and accurate. AED entry was excluded if it was recently initiated within six months or less in order to access longer retention rates. A total of 828 AED exposures were obtained (LEV =96, LMT=251, OXC=97, TPM=156, ZNS=128) for both partial and generalized epilepsy treatment. The overall retention rate of these AEDs was 58.82% (487 of 828). At two years, retention rate was highest with LMT (74.10%), followed by ZNS (60.94%), OXC (58.76%), LEV (53.57%), and TPM (58.76%). When these AEDs were discontinued, it was mainly due to inefficacy (29.12%) and sedating side-effects (20.59%), and commonly within 6 months (79.48%) into therapy. Several important AED specific side-effects leading to discontinuation of AEDs were noted, including behavioral or irritability from LEV (41.30% of discontinuation causes), rash from LMT (18%) and OXC (14.29%), GI upset from OXC (9.52%) and ZNS (9.80%), hyponatremia from OXC (7.14%), kidney stones from TPM (3.41%), and ZNS (5.88%). Discontinuation due to sedation and fatigue was highest with TPM (27.27%) and lowest with OXC (7.14%). Comparing retention rate of newer AEDs provides useful insight into their tolerability and efficacy in the treatment of epilepsy. This study shows highest retention rate at 1 year and 2 years with lamotrigine and lowest with topiramate (p[lt]0.001). Beside ineffectiveness, the leading cause of discontinuation for each AED was irritability or other behavioral effects for LEV, rash for LMT and OXC, sedation for TPM and ZNS.