THE FATE OF FD&C BLUE NO. 2 IN RATS

¹ Division of Pharmacology, Food and Drug Administration, United States Department of Health, Education and Welfare, Washington, D.C.

The fate of FD&C blue no. 2 was studied in rats after oral and intravenous administration of material labeled with S³⁵. After intravenous injections, an average of 23% of the radioactivity was excreted in the urine after 30 mm and increased until 63% was accounted for after 6 hr. The amount found in the bile accounted for about 10% of the dose with no significant increase after the first hour. Isatin-5-sulfonic acid and 5-sulfoanthranilic acid appeared in the urine after 2 hr. After 6 hr, two-thirds of the urinary radioactivity remained as unchanged dye. The results after oral administration of the dye at several levels suggested that it was poorly absorbed from the alimentary tract, with less than 3% of the radioactivity appearing in the urine after 3 days. Column and paper chromatography of the urine indicated that the radioactivity was composed of the unchanged dye and its two oxidative products. The amounts found in the feces were due to unabsorbed dye rather than to biliary excretion. Orally administered 5-sulfoanthranilic acid was absorbed to a greater extent than the dye; an average of 24% appeared in the urine after 2 days.