Dry powder coating of pharmaceutical tablets

A novel dry powder coating process has been developed for coating pharmaceutical tablets without organic solvent or water. A series of dry powder formulations were designed for several pharmaceutical applications including fast release, moisture protective films, delayed release and sustained release. Conventional coating pharmaceutical polymers, such as such as Eudragit RS, Eudragit RL, Eudragit L, Eudragit E PO and Acryl-eze MP, in combination with standard excipients were successfully coated onto tablets of different surface properties by electrostatic deposition using conventional non-perforated coating pans. In the process, the uncoated tablets were heated to a defined temperature. Then the dry powder formulation and other ingredients (if required) were sprayed separately onto the surface of tablets in the rotating coating pan using a electrostatical spray gun and appropriate processing equipment (as needed) under controlled conditions. After the electrostatic powder deposition, the coated tablets were cured completely. Suitable operating parameters for the dry powder coating process were determined by optimizing the spraying speed, temperature, atomization pressure and curing time. The surface of polymer film was visually examined by scanning electron and optical microscopy. Drug dissolution study of both coated and uncoated tablets were also carried out according to the method described in the USP (Apparatus 2; 37°C; 50 rpm). The results showed that the coated tablet surface was very uniform, meeting the quality requirements for commercial manufacturing. The drug release profiles were comparable to the target profiles and also to the expected profiles generated from solvent or aqueous coating. The benefits of electrostatic dry powder coating of pharmaceutical tablets include significant energy savings, simple equipment, and reduction of air handling and cleaning requirements leading to lower capital and operation costs. In view of the environmental and cost benefits, dry powder coating using conventional exicipients and equipment will likely to be commercialized in the pharmaceutical industry.