ABSTRACT
Coloring agents are widely used in the pharmaceutical industry and are an important component of many oral solid dosage forms. A coloring agent or colorant may be dened as an excipient that imparts color when added to a drug product. Colorants may be incorporated into solid dosage forms by adding them directly to the dosage form (e.g., adding a colorant to a tablet granulation), incorporating the colorant into capsule shells, and by adding the colorant to a coating formulation that
Introduction .................................................................................................................................... 151 Coloring Agents Used in Film Coating .......................................................................................... 153
Dyes........................................................................................................................................... 153 Pigments .................................................................................................................................... 153
Aluminum Lakes .................................................................................................................. 153 Iron Oxides ........................................................................................................................... 154 Titanium Dioxide.................................................................................................................. 154 Talc ....................................................................................................................................... 154 Glyceryl Monostearate ......................................................................................................... 154 Pearlescent Pigments ............................................................................................................ 155
Regulation of Coloring Agents .................................................................................................. 155 Properties of Coloring Agents ........................................................................................................ 155
Dyes........................................................................................................................................... 155 Pigments .................................................................................................................................... 155
Inuence of Coloring Agents on Polymer Coating Dispersions .................................................... 159 Solution and Colloidal Interactions ........................................................................................... 159 Formulation of Pigmented Coating Dispersions ....................................................................... 162
Inuence of Coloring Agents on Polymer Films and Coated Products ......................................... 163 Appearance ................................................................................................................................ 163 Light Protection ......................................................................................................................... 165 Mechanical Properties ............................................................................................................... 167 Thermal Properties .................................................................................................................... 169 Permeability .............................................................................................................................. 170 Drug Release ............................................................................................................................. 170 Adhesive Properties ................................................................................................................... 172
Summary ........................................................................................................................................ 173 References ...................................................................................................................................... 173
would be applied onto the surface of a drug product. Coloring agents may be added to pharmaceutical coatings for a number of reasons, including the following:
1. To enhance product appearance, aesthetic appeal, and product elegance 2. To improve or facilitate product identication for the manufacturer, health care profes-
sional, and patient 3. To provide protection from light for photosensitive compounds 4. To provide a brand image and help differentiate the drug product from competitive products 5. To help reduce or prevent counterfeiting
Although coloring agents do not provide any direct therapeutic effects by improving the appearance of the drug product, they can contribute to increasing patient compliance. The use of coloring agents helps to provide drug products with a distinct appearance, which makes it easier for the pharmacist and patient to distinguish between different drug products, thereby reducing the possibility of dispensing and medication errors. Patients taking several different medications will nd them easier to distinguish if they have different colors. A unique appearance also contributes to enhancing the brand image of a drug product, which may provide a signicant marketing advantage over competitive products. In combination with other factors that can be used to increase the uniqueness of the drug product, such as shape and markings, the addition of color can help to make it more dif-cult to counterfeit drug products.
