An Innovative Excipient System for Film Coating

Colorcon’s film-coating excipient system, Opadry QX, won the 2017 CPhI Pharma Award for Excellence in Pharma: Excipients. Kelly Boyer, General Manager Film Coating, at Colorcon spoke to Pharmaceutical Technology about the challenges in tablet coating, the requirements of continuous coating, and how to improve process efficiency and product quality.

PharmTech: What are the challenges in tablet coating, and why is reproducibility often an issue?

Boyer: The challenges faced are varied, but are primarily related to the tablet core, the coating formulation, and the process. Working with different coating equipment, and yet achieving reproducible coating quality, is a major challenge for pharmaceutical manufacturers.

Companies are faced with a multitude of obstacles as tableting and coating processes move from development through scale-up to production. Challenges multiply with validation studies or when transferring production from site-to-site and across continents. For instance, in the Asia Pacific region and some parts of Europe, coating equipment tends to have much lower airflow than in the United States. Latin America, meanwhile, still uses many conventional solid wall pans, which have low airflow and poor temperature control. The coating formulation needs to be flexible and robust to withstand these types of variables and still result in a uniform, high-quality final appearance that does not vary from batch to batch.

PharmTech: Could you tell us more about Opadry QX and how it is different from other coating excipients?

Boyer: Opadry QX advanced the science of film coating formulation through the inclusion of polyvinyl alcohol–polyethylene glycol (PVA–PEG) graft copolymer, which is recognized as a material with good film coating properties. The coating formulation has been fully optimized and tested on a range of equipment across the world, using a variety of tablets, some containing challenging active ingredients.

Opadry QX can be formulated at solids concentrations up to 35% while maintaining low dispersion viscosity. This feature enables faster preparation and coating application process times, down to nearly half that for traditional HPMC-based coatings.  This improved processing means tablets are exposed for far less time to the tumbling, heat, and moisture associated with the rigors of the coating process. 

For example, a multi-national generic manufacturer recently expressed the need to match the appearance of the innovator containing a highly friable core. Production would take place in an area of the world where equipment airflow capacity and moisture sensitivity is a challenge. In this example, shifting from an HPMC-based coating to Opadry QX proved to be the exact solution needed to provide both the reproducibility and product quality required. As an added benefit, even greater productivity than anticipated was realized by switching the coating. And with Colorcon’s global reach through our regional laboratories and technical service, support was provided directly to implement this change quickly and efficiently.

PharmTech: What are the advantages of continuous coating compared to batch production?

Boyer: Continuous coating enables faster cycle times with increased process flexibility and throughput. Regulatory agencies, such as FDA, also see the benefits in improving manufacturing processes to reduce production interruptions and product failures. Continuous coaters are designed to run for days without interruption, with tablet throughput ranging from 210 kg to 1000 kg per hour, and with large volumes of drying air and spray rates of more than a liter per minute. Developing the optimal coating formulation and process conditions that will consistently result in the production of high-quality film-coated tablets in a continuous processing environment is essential. Compared to batch coating processes, continuous film coating processes allow for fast coating times and have been shown to provide excellent color uniformity due to a shallower tablet bed depth and increased frequency of tablet presentations to the spray zone. It’s important to remember that the process may start as batch before being scaled up to continuous; therefore, it’s vital to have a flexible coating system that can be used across a broad range of equipment.

PharmTech: What are the key requirements for continuous coating and how does Opadry QX address these needs?

Boyer: The improved coating uniformity achievable with continuous coating allows manufacturers to take full advantage of increased solids concentrations possible with Opadry QX to improve throughput rates. The flexibility of Opadry QX to be applied at solids concentrations as high as 35% makes it particularly suited for continuous or semi-continuous processing. Films are applied faster, color uniformity reached earlier, and the final coated tablets have a uniform, defect-free finish, making a positive contribution to product quality. Furthermore, Colorcon recently presented studies, in collaboration with ILC Dover, to address the growing need for on-demand preparation of the coating dispersion.