21 CFR 74.1104 - D&C Blue No. 4.
(1) The color additive D&C Blue No. 4 is principally the diammonium salt of ethyl[4-[p[ethyl(m- sulfobenzyl)ami-no]-α-(o- sulfophenyl)benzylidene]-2,5-cyclo-hexadien-1-ylidene] (m- sulfobenzyl) ammonium hydroxide inner salt with smaller amounts of the isomeric diammonium salts of ethyl [4-[p-[ethyl(p- sulfobenzyl) amino]-α-(o- sulfophenyl) benzylidene]-2,5-cyclohexadien - 1-ylidene](p- sulfobenzyl) ammonium hydroxide inner salt and ethyl[4-[p-[ethyl (o- sulfobenzyl)amino]-α-(o- sulfophenyl) benzylidene]-2,5-cyclohexadien-1-ylidene] (o- sulfobenzyl) ammonium hydroxide inner salt.
(2) Color additive mixtures for use in externally applied drugs made with D&C Blue No. 4 may contain only those diluents that are suitable and that are listed in part 73 of this chapter for use in color additive mixtures for coloring externally applied drugs.
(b)Specifications. D&C Blue No. 4 shall conform to the following specifications and shall be free from impurities other than those named to the extent that such impurities may be avoided by good manufacturing practice:
(c)Uses and restrictions. D&C Blue No. 4 may be safely used in externally applied drugs in amounts consistent with good manufacturing practice.