Hyponatraemia during carbamazepine therapy in children

A boy is described who developed clinically significant hyponatraemia during carbamazepine treatment. After eight years treatment with carbamazepine the boy began to have grand mal seizures which were clearly related to hyponatraemia. This disappeared when carbamazepine was stopped. Afterwards the boy was more alert and did not have seizures any more. The serum concentrations of sodium and potassium and serum osmolality were subsequently investigated in 94 other children under our care who received carbamazepine. No abnormal values were found. Serum osmolality was not related to serum concentration of carbamazepine in these children. It is concluded that water intoxication during carbamazepine treatment can occur also during childhood, but that it is probably not a common side effect.