THE ABSORPTION, FATE AND EXCRETION OF CITRUS RED NO. 2 (2,5-DIMETHOXYPHENYL-AZO-2-NAPHTHOL) AND EXT. D&C RED NO. 14 (1-XYLYLAZO-2-NAPHTHOL)

¹ Department of Pharmacology, University of Miami School of Medicine, Coral Gables, Florida

When Citrus Red No. 2 was administered to animals in doses of 20 to 2 mg in corn oil solution, 5 to 7% of the administered dye was recovered in the feces in 48 hr. When the dose was reduced to 0.5 mg, no dye was found. When the dye was administered as a dry mixture, 26.3% was found in the feces. Rabbits and dogs exhibited a similar picture.

The picture of fecal excretion with External D&C Red No. 14 was essentially the same as found with Citrus Red No. 2 in rats, rabbits and dogs.

In vitro incubation of emulsions of both dyes with the intestinal contents of the rat, rabbit and dog resulted in destruction of the dye by the bacterial flora.

After a single dose of either Citrus Red No. 2 or External D&C Red No. 14, small amounts of dye were found in the fat, but none in other tissues. Repeated administration of either of these dyes resulted in the gradual reduction in the concentration of dye in the fat and finally its disappearance altogether after a period of 7 to 10 days. This phenomenon is discussed from the point of view of adaptive changes of liver enzymes.

By chromatographic procedures, small amounts of 1-amino-2-naphthyl sulfate were identified in the urine of rats administered either External D&C Red No. 14 or Citrus Red No. 2. This demonstrates that both these azo dyes are reduced at the azo linkage in the animal body. The significance of this observation from the point of view of the production of bladder cancer is discussed.

External D&C Red No. 14 prepared from C¹⁴-labeled 2-naphthol was administered to rats. Over all, 86.2% of the total radioactivity appeared in the feces and 13.8% appeared in the urine. Although excretion of the dye itself was complete in 24 hours, small amounts of radioactivity continued to be excreted in the urine and feces for 27 days.

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