(T1430-03-16) Comparison of Film Coating Weight, Color Uniformity and Throughput of Tablets Coated in High Speed Semi Continuous Coater and Traditional Pan Coater Using Titanium Dioxide Free Film Coating Systems

Purpose: Titanium dioxide (TiO₂) has long been a crucial ingredient in countless products as an opacifier and coloring agent. This unique white mineral ingredient with a high refractive index, density, and brightness improves tablets and capsules' light stability, safety, and efficacy, even at low concentrations. However, in recent years, TiO₂ has become a controversial ingredient among safety agencies and consumers and is no longer considered safe when used as a food additive. Transitioning from a TiO₂-based traditional coating to a TF film coating system requires specific formulations and process adjustments. It may require adjustments in solids content, wider color variation, and higher coating weight gain to provide uniform and equivalent coverage to TiO₂ based film coating. Those adjustments may negatively impact process time and economics, considering higher weight gain requires longer process times and potential impact on productivity. The objective of this study was to evaluate the titanium-free film coating in a high-speed semi-continuous coater (GEA ConsiGma™ Coater, GEA Systems) compared to a traditional batch coater and to assess the TF coating performance and opacity against the traditional TiO₂-based film coating system.

Methods: Aqueous dispersions of fully formulated TF film coating systems were evaluated at varying solid concentrations of 12.5% (A), 17.5% (B), and 30.0% (C). Corresponding TiO₂-based coatings were used as standards for their respective titanium-free versions. Tablets at different weight gains were sampled to determine the minimum weight gain required for a uniform and opaque coverage. A photosensitive active was incorporated into the core to test the stability of the product. The coating trials were conducted in a traditional batch coater fitted with a 15" perforated pan and compared against the ConsiGma coater equipped with a 160mm wheel. Tablets were sampled at 3%, 4%, and 5% weight gain and tested for color uniformity using a reflectance spectrophotometer (DataColor^TM 650), surface roughness using an optical profilometer (Nanovea^TM), and tablet gloss (surface analysis system, Tricor systems). The color stability study was conducted in accordance with International Council for Harmonization (ICH) guidelines (Q1B) in a light booth (Gardner byko-spectra Basic light booth) with D65/ID65 daylight simulating bulb. The stability of the active was assessed by measuring the degradation product using HPLC. Uncoated tablets were used as control samples, and TF coated tablets were compared against TiO₂-coated tablets.

Results: The comparison of different TF film coating formulations exhibited a wide range of viscosity and desirable conditions for coating application (Figure 1). Tablets coated with TF coating system in the high-speed semi-continuous coater (GEA ConsiGma™ Coater) showed improved aesthetics, coating uniformity and a positive impact on productivity, reducing processing time even at higher weight gains when compared to a traditional batch coater (Figure 2). The opacity study allowed us to determine the recommended weight gain for a TF film coated product to perform similarly to a TiO₂-based traditional film coating.

Conclusion: The careful selection of the film coating formulation and coating equipment resulted in a very significant impact in resolving the higher processing time related to the higher coating weight gain impact, which is an inherent characteristic of formulations titanium dioxide-free and necessary to compensate and improve the film opacity and the pharmaceutical products stability.

Figure 1: Rheological assessment of TF film coating formulations



Figure 2: Typical coating process times of TiO2 and TF film coating systems in a batch coater (30" pan, 40KG batch size)