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-Schönlein nephritis. The patient was known to have a generalized idiopathic epilepsy and was on 2,000 mg/day of sodium valproate. After exclusion of other causes such as hypothyroidism and adrenal insufficiency, we considered sodium valproate as the cause of the hyponatremia. Repeated water loading tests performed at different dosages of this drug confirmed that the ability to excrete water was reduced in a dose dependent manner. We conclude that sodium valproate can cause an SIADH-like syndrome with hyponatremia and that serum sodium levels have to be monitored during treatment with high dosages of this drug.