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T Tablets & Capsules April 2017 21 coating Coating optimization: Equipment features to prevent defects Caterina Funaro and Massimo Malavolti IMA The process of coating pharmaceuticals must be carefully controlled to obtain a high-quality end product. This article high- lights some equipment features that can help you reach that goal. he first consideration before coating begins is core shape. A flat profile, for example, is a poor choice because it will allow many of the tablets to stick together, a defect called twinning. The next consideration is the coating itself, which must comprise the appropriate ingredients at the specified percentages. Ideally, the coating optimizes wettability and elasticity while delivering solids at the maximum rate without having an impact on viscosity. Producing high-quality coated tablets also requires identifying the optimal process parameters, which must be in harmony and kept under control. That means combining efficient spray technology with the appro- priate mixing baffles and a high-performance drying system. Also critical is a user-friendly control system to manage the process parameters, along with proper maintenance and calibration. Doing so ensures not only coating quality, but minimizes coating losses. Below are some brief examples of how customizing a coating system's hardware and software can help you obtain a high-quality result. Foam Anyone with coating experience knows that the pres- ence of foam in the coating suspension can lead to prob- lems with the final product. Most of today's coating sys- tems prevent foam by combining the coating powder and liquid—usually water—using a method that minimizes air entrainment. Nevertheless, as you near the end of a batch run, it's possible that the agitator in the coating tank will breach the surface, entrain air, and generate foam. To avoid that, place a level sensor in the tank and connect it to a switch that shuts off the agitator automatically when the suspension is no longer in contact with the sensor. Gun position The improper orientation of the spray guns and/or the distance between them and tablet bed can have a big impact on results, including overly wet tablets and tablets with surface defects. In many cases, operators must moni- tor the process and adjust the guns manually. If that's how you operate, consider using a system that adjusts the guns automatically, such as the one our company offers. It uses a laser to detect the orientation of the guns and the gun-to-bed distance throughout the process and adjusts them as needed to keep prevent defects. IMA's Effecta coating system has a perforated pan with baffles at its center to optimize mixing of the cores. A fully perforated pan