Developing a film-coating color for an oral, solid-dose pharmaceutical product comes with some challenges. Creating and choosing
the color for an instant-release coating for a new product not only involves working with associates across several areas
such as research and development, manufacturing, and marketing, but also often includes the manual process of formulating
individual coatings to evaluate color options. Automating the process of developing and evaluating a color formulation helps
to save time and reduce costs when developing an oral solid dosage product. This article examines currently applied manual
color systems and a new automated color system using excipient technology and specialized software tools.
COURTESY OF THE AUTHOR
Manual color systems
The manual film-coating color-development process can be difficult and time-consuming. Developing a film-coating color involves
the selection and formulation of the optimal ratio of polymer to plasticizer to achieve a successful coating. The process
of determining the correct pigments, pigment concentrations, and pigment combinations needed to reach a desired color can
be tedious. Pigment selection is further complicated by taking into consideration the colorants needed to reach a final color
and how the regulatory status of each colorant affects acceptability in different regions of the world. This situation is
often the case with iron oxides and aluminum lakes.
Once a film-coating color formulation has been finalized, the process of making the formulation for use in production has
to be considered and developed. This process often involves preparing a suspension by adding separately each of the individual
ingredients, which include polymers, plasticizers, and pigments. Depending on the film-coating ingredients, as with hypromellose,
for example, this process can be time-consuming. In addition, specific colorants may need to be individually processed before
use, for example, by reducing the particle size of ingredients, to optimize performance. Colorant testing to ensure that the
final film-coating color is consistent from batch to batch adds further complexity.
Immediate-release film coatings
To simplify this process, BASF (Ludwigshafen, Germany) created a new fully formulated color-coating system for immediate release
film-coatings using a polyvinyl alcohol polymer grafted onto polyethylene glycol in a ratio of approximately 75:25 (Kollicoat
IR). The coatings are manufactured using seven base colors and are fully formulated using globally accepted pigments (i.e.,
those in accordance with: the US Code of Federal Regulation, Title 21, "Food and Drugs"; the BIRYO limits on trace amounts as specified by Japan's Ministry of Health, Labor and Welfare;
and the Dictionary of Pharmaceutical Excipients (Japan)) in combination with a manufacturing process that results in coating granules that are easy to use. Examples of each
of the seven base colors are provided in Figure 1.
Figure 1 (FIGURES 1 AND 2 ARE COURTESY OF THE AUTHOR)
As described in Figure 2, each pigment is brought into suspension together with polymers to form seven base color preparations.
These preparations form solid dispersions of pigments in the polymer. The free-flowing, nearly dust-free granules, are readily
dispersible in water and can be easily combined to create color options. The basic components are combined onsite to form
the desired color. A coating system of the desired color is produced, and the coating system is readily dispersible to form
the coating suspension.