Abstracts

Oxcarbazepine (OXC) has been an effective and usually well tolerated drug in the treatment of partial and 2[deg] GTC sz. However, in clinical trials, clinically significant hyponatremia (sodium (Na+)[lt]125mmol/L) was reported in 2.5% of pts treated with OXC. The incidence of clinically significant hyponatremia increases with age. It is for these reasons we followed the sodium levels fairly closely, especially when there was a decrease from the pt[apos]s baseline Na+. For our study, we chose to evaluate the results of our pts[apos] compliance with fluid restriction (FR). We also evaluated if any pts required withdrawal from OXC due to hyponatremia. We questioned whether there was any difference or greater risk for developing hyponatremia if pts were switched from carbamazepine (CBZ) to OXC versus being on the two drugs together. In addition, we attempted to determine if the BUN/creatinine ratio was a reliable tool for monitoring efficacy of fluid restriction in improving the hyponatremia. We reviewed the clinical data of the first 119 pts on OXC, randomly chosen from our clinic. In our statistical analysis, we included 101/119. The pts were excluded from the project if they were on OXC for less then 2 months, or there was insufficient data to review because of pt non-compliance in obtaining labs. 101/119 pts[apos] clinical data were reviewed. 31/101 (30%) pts (mean age 43 yrs) were found to have some degree of hyponatremia (Na+ [lt] 135mmol/L). 27/101 (27%) had Na+ [lt]133mmol/L and were instructed on an 1800ml/day FR and 3 of these 27 pts had on occasion clinically significant hyponatremia ([lt]125 mmol/L) treated with tighter FR of 1500ml/day. 16/27 (59%) were females (mean age 46 yrs) and 11/27 (41%) were males (mean age 43 yrs). 17/27 (63%) pts were started as initial therapy or add-on to AED[apos]s other than CBZ. 7/27 (26%) pts were switched from CBZ to OXC overnight. 1/27 (4%) was switched over four days. 2/27 (7%) pts were on both CBZ and OXC for a longer period of time; 1/2 of these pts developed hyponatremia while taking both and continued on OXC after the CBZ was stopped without a significant change in Na+. Neither pt had low Na+ on CBZ monotherapy. The pts were continued on OXC, maintaining Na+ levels in the 130[apos]s. Compliance to the FR was evaluated by following Na+ and BUN/creatinine ratios; pts with ratios [underline][gt][/underline] 15 suggested compliance. 18/27 (67%) pts had B/C ratios above 15. 6/27 (22%) pts were considered partially compliant, 1/27 (4%) pt non-compliant and 2/27 (7%) pts have incomplete data as FR was only recently initiated. Fluid restriction is an effective treatment in OXC induced hyponatremia. These patients can be monitored with serum Na+ and BUN/creatinine ratios and frequent reminders that FR needs to be ongoing. In this group of 27 hyponatremic patients, none had to be discontinued from OXC therapy. (Supported by The Comprehensive Epilepsy Care Center For Children And Adults.)