Oxcarbazepine-induced hyponatremia and the regulation of serum sodium after replacing carbamazepine with oxcarbazepine in children

While severe hyponatremia is reported to be more frequent in adults treated with oxcarbazepine (OXC) than with carbamazepine (CBZ), there is not sufficient data about the incidence of hyponatremia in childhood during treatment with OXC. We evaluated changes in serum electrolyte balance in 75 children with epilepsy before and during treatment with OXC and after replacing carbamazepine (CBZ) therapy with OXC therapy. All patients had normal sodium serum levels at the onset of OXC. During treatment with OXC we found hyponatremia (Na+< 135 mmol/l) without clinical symptoms in 26.6% of the children (n = 20), sodium levels below 125 mmol/l were observed in 2 children (2.6%). Clinically relevant hyponatremia occurred in one girl only (1.3%). In a subgroup of 27 children, in whom CBZ was directly replaced with OXC, hyponatremia without symptoms was found in one child under CBZ (3.7%) and in six children under OXC (22.2%). Dosage of OXC, serum levels of the active metabolite of OXC, antiepileptic comedication or patients' age and gender were of no predictive value for the development of hyponatremia. Electrolytes should be measured before establishing OXC and if clinically relevant side effects occur.