The displacement of bilirubin from albumin by furosemide

Since furosemide, a sulfonamide diuretic, has been recommended for use in the newborn infant, a study was made of its effect on the bilirubin-binding capacity of albumin. Furosemide was compared to sulfisoxazole, a known displacer of bilirubin, by means of three methods. First, aliquots of whole blood from 20 icteric infants were diluted in phosphate buffer along with expected clinical concentrations of furosemide and sulfisoxazole. The red cells and globulins were then isolated and bilirubin concentrations were measured in these two fractions. The addition of Furosemide resulted in the displacement of bilirubin from albumin to red cells and globulins. Mole for mole, furosemide displaced bilirubin about as well as sulfisoxazole. Second, the hydroxybenzeneazobenzoic acid dye binding test of Porter and twaters was performed using the sera of eight jaundiced newborn infants. The mean dye binding capacity of the sera was significantly reduced with the addition of furosemide to a final concentration of 2 mug/ml. Third, the administration of furosemide (5 mg/kg) or sulfisoxazole (50 mg/kg) to adult Gunn rats resulted in a significant fall in mean serum bilirubin concentration compared to saline controls. Furosemide, like sulfisoxazole, is a potent displacer of bilirubin and should be used with caution in jaundiced infants.