Higher dosages of OXC and the number of combination antiepileptic drugs may increase the risk of OXC-induced hyponatremia in patients with epilepsy. Most patients are asymptomatic, but if symptoms of hyponatremia, such as headache, general malaise, gait disturbance, and somnolence, are suspected, the serum sodium level should be measured; it may be necessary to decrease the OXC dose or to discontinue the drug.