Comparison of Serum Bilirubin Levels in Humans and Two Monogastric Animal Species After a Single Administration of Sulfisoxazole

Administration of sulfonamides during periods of hepatobiliary failure or hepatic immaturity increases the toxic potential of unconjugated or indirect bilirubin. A small but statistically significant increase of indirect, or unconjugated bilirubin was noted in dogs after oral administration of sulfisoxazole (100 mg/kg). A similar increase was not observed in swine after oral or intravenous administration of sulfisoxazole (100 mg/kg) or in humans (∼28 mg/kg) after oral administration or in dogs (100 mg/kg) after intravenous administration. Total and conjugated bilirubin showed small but statistically significant increases and were significantly correlated in dogs after oral and intravenous administration of sulfisoxazole (100 mg/kg) and in swine after oral administration of sulfisoxazole (100 mg/kg). There was a significant negative correlation between conjugated and indirect bilirubin, while total bilirubin increased in dogs after oral and intravenous administration of sulfisoxazole. These data illustrate a difference in species and administration route when attempting to assess the potential toxicity of bilirubin.