Coating Coin-Shaped Tablet Cores: A Downstream Technology Solution to Reduce Tablet Capping
Tablet capping or delamination is a major concern in pharmaceutical tablet manufacturing. In the effort to reduce this phenomenon, coin-shaped or flat-faced tablet cores offer several benefits over biconvex forms but have traditionally been difficult to coat. GEA Pharma & Healthcare has developed innovative technology addressing this issue effectively.
Understanding Tablet Capping
Tablet capping refers to the detachment of a cross-sectional fragment from the tablet's surface, occurring post-compression and leading to product rejection. The deformation behavior of tablet ingredients determines the extent to which a tablet is prone to capping. Materials that deform plastically or undergo brittle fracture present a lower capping risk, while those that deform elastically or viscoelastically are more susceptible, especially at high production speeds. This issue is exacerbated when the API itself shows this behavior, particularly at high concentrations, and often becomes apparent only during commercial-scale production. Changing the formulation can be a solution, but this is often not viable for registered products or is limited in the case of high-dose products.
Influence of Pre-Tableting Processes
The processes preceding tableting also influence capping tendencies. Direct compression can increase capping risk due to higher fines content. In contrast, wet granulation, particularly spray granulation, minimizes capping by evenly distributing binders. Entrapped air during compression can also cause capping, which GEA’s Air Compensator addresses by augmenting pre-compression force and improving tablet mechanical strength.
The Role of Tablet Shape
Dr. Harald Stahl, Senior Director for Innovation and Strategy at GEA, notes that traditional coin-shaped tablets, which are ideal for reducing capping, were replaced by biconvex forms, as these are easier to coat for aesthetic reasons and ease of swallowing. However, the biconvex shape is more prone to capping due to weaker Van der Waals forces at the radial edges, leading to non-uniform compression and increased capping risk.
Innovative Coating Technology
Today however, it is feasible to coat coin-shaped tablets, using GEA’s advanced coating technology. This versatile system, suitable for research, clinical, and full-scale production, incorporates a perforated wheel and air knives to create a stable, free-falling cascade of tablet cores. This method enhances drying efficiency and significantly reduces coating time from 90 minutes to under 10 minutes, compared to conventional pan coating processes.
Practical Applications
Initial tests with flat-faced placebo cores have yielded promising results. Although these tablets were not originally designed for coating, the GEA coater successfully managed to coat a somewhat fragile and moisture-sensitive product without damage. Leslie Van Eeckhout, Senior Process Specialist at GEA, emphasizes that while further testing is needed, the GEA coater is capable of handling various shapes and dimensions, making it a viable solution to tablet capping issues.
