HYPONATREMIA DUE TO SODIUM VALPROATE

We describe a 50-year-old male patient with hyponatremia (serum sodium level, 128 mEq/L) discovered during routine follow-up for Henoch-Scho nlein nephritis. The patient was known to have a generalized idiopathi c epilepsy and was on 2,000 mg/day of sodium valproate. After exclusio n of other causes such as hypothyroidism and adrenal insufficiency, we considered sodium valproate as the cause of the hyponatremia. Repeate d water loading tests performed at different dosages of this drug conf irmed that the ability to excrete water was reduced in a dose dependen t manner. We conclude that sodium valproate can cause an SIADH-like sy ndrome with hyponatremia and that serum sodium levels have to be monit ored during treatment with high dosages of this drug.