Frequency of and risk factors for oxcarbazepine-induced severe and symptomatic hyponatremia

Hyponatremia (defined as a serum sodium level < 134 mmol/L) is the most common electrolyte abnormality in hospitalized patients. Certain drugs (eg, diuretics, antidepressants, and antiepileptics) have been implicated as established causes of either asymptomatic or symptomatic hyponatremia. However, hyponatremia occasionally may develop in the course of treatment with drugs used in everyday clinical practice (eg, newer antihypertensive agents, antibiotics, and proton pump inhibitors). Physicians may not always give proper attention in time to undesirable drug-induced hyponatremia. Effective clinical management can be handled through awareness of the adverse effect of certain pharmaceutical compounds on serum sodium levels. Here, we review clinical information about the incidence of hyponatremia associated with specific drug treatment and discuss the underlying pathophysiologic mechanisms.

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.