Published Online: Wednesday, August 1, 2007
I have a formulation for liothyronine capsules that requires aliquot dilution technique. A "dye" is part of the formulation. What does that mean?
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Food, Drug, and Cosmetic (FD&C) aluminum lake dyes often are used to prove adequate dispersion of powders triturated for compounding of capsules. Aluminum lake dyes are water-insoluble forms of water-soluble dyes prepared by adsorbing a salt of the dye (usually sodium or potassium) onto a finely divided substrate of hydrated alumina, then treating with soluble aluminum salt. After purification and drying, the aluminum lake dye can be used to color powder triturations. Generally, a pinch (1 mg or less) of one of the FD&C aluminum lake dyes is sufficient to color a mass of material for 100 or 200 #1 capsules. The dye is added prior to trituration or prior to employing another mixing technique, such as using a V-blender or tumbling the mass in a sealed plastic bag. Use of a brightly colored, contrasting dye such as FD&C aluminum lake red #40 ("Allura red AC") or FD&C aluminum lake blue #1 ("Brilliant blue FCF") can be advantageous. Particle reduction before adding the coloring agent and final mixing is suggested, because the coloring agent can be difficult to remove from a ceramic or Wedgwood mortar and pestle. Food dyes should not be used for this purpose, primarily because they are not approved as drug additives and because they usually are liquid and will cause powder agglomeration.