Abstracts

Rationale: Oxcarbazepine (OXC) is a new-generation antiepileptic drug (AED) and, recently the usage has increased. Hyponatremia, side effect for OXC treatment is well known. But, the prevalence of hyponatremia in OXC-treated patients varied greatly (23% to 73.3%) and the results were derived from relatively small studies. The purposes of this study are to evaluate the frequency and determine the risk factors for hyponatremia in patients with epilepsy treated with oxcarbazepine (OXC). Methods: One-hundred eighty four adult patients with epilepsy who received OXC therapy were enrolled in this study. We used cross-section study design. Inclusion criteria were 1) epilepsy patient with OXC treatment, 2) age 16 years or older, 3) active out-patients in the period 2010 to 2012, 4) at least one sodium level documented in that period. Demographic and clinical data were collected by the review of medical records. In statistical analysis, to compare serum sodium level and continuous variables (age, OXC dose, and the number of current AEDs being used) were assessed using univariate linear regression. Using ANOVA, normal sodium group, hyponatremia (Na+ ≤ 134 mEq/L) group, and severe hyponatremia group (Na+ ≤ 128 mEq/L) were analyzed to compare the age, sex, other medication. Results: A total of 184 patients with epilepsy 16 year and older and exposed to OXC with sodium documented were included in the analysis. The mean age of patients was 56 ± 19.1 (16-95), the mean OXC daily dose was 960.76 ± 517.28mg (150-4200), the mean number of other AEDs was 2.0 ± 1.12 (1-8), and the mean serum sodium concentration was 136.3 ± 6.44 mEq/L. Univariate linear regression showed that two variable were significantly associated with the serum level of sodium concentration. They were older age (p = 0.003) and higher number of other AEDs (p = 0.021). Multivariate analysis using linear regression analysis was performed with the variable which had been significant (p < 0.05) in univariate analysis. Multivariate linear regression analysis revealed that older age and higher number of other AEDs were independently associated with lower serum sodium level. The comparative results of the a few clinical features between patient without hyponatremia, with hyponatremia, and with severe hyponatremia using by ANOVA showed that two features were significantly associated. They were older age (p < 0.0001) and other non-AEDs medications (antiplatelet, NSAID, diuretics, opiate, and TCA, p < 0.0001). Conclusions: Older age, the number of combination AEDs, and other non-AEDs medications may increase the risk of OXC-induced hyponatremia in patient with epilepsy.