Severe hyponatremia with indomethacin--a more serious toxicity than previously realized?

Five low-birth-weight neonates, ranging from 580 to 1,430 g, developed clinically significant hyponatremia (less than 130 mg/dl) within 48 h after being given indomethacin for patent ductus arteriosus closure. The extent of this hyponatremia is much more severe than previously reported. This group of infants is compared to another group of 5 patients who received indomethacin but did not develop severe hyponatremia. Several possible explanations for the observed differences are explored.