Hyponatremia from oxcarbazepine and carbamazepine.

The authors examined sodium concentrations from 97 oxcarbazepine-treated (OXC) and 451 carbamazepine-treated (CBZ) patients with epilepsy using cross-section and follow-up studies. The frequency of hyponatremia (Na+ < or = 134 mEq/L) was 29.9% among OXC-treated patients and 13.5% among CBZ-treated patients (p < 0.0001). Hyponatremia (Na+ < or = 128 mEq/L) was severe: 12.4% of OXC-treated patients and 2.8% of CBZ-treated patients (p < 0.001). Advanced age was a risk factor for hyponatremia. Hyponatremia, once present, persisted in both groups.