Study of Different Technologies for Film Coating of Drug Layered Pellets Using Ethylcellulose as Functional Polymer

The research project focused on the study of different technologies for film coating of pellets using ethylcellulose as barrier-membrane coating polymer. In particular, two different approaches were investigated: the conventional aqueous film coating and the dry powder coating methods. The research carried out during the first part of the PhD provided a comprehensive study of the conventional aqueous film coating process of guaifenesin-loaded pellets in order to understand the variables affecting the drug migration through the barrier-membrane film coating and thus the stability over time of the final dosage form. The analysed process comprised the drug layering followed by the film coating technique in a Wurster fluid bed. The effect of curing conditions, drug loading and coating level and of the drug-layering solution on the technological properties of pellets was fully evaluated. In the second part of the research, an innovative dry powder coating technology was developed to apply the functional ethylcellulose based coating upon pellets avoiding the use of solvents (neither organic solvents nor water). In particular, the study was designed along three steps: i) Preparation of free films to evaluate the film formation process and to achieve the minimum film forming temperature of the coating formula; ii) Powder coating process of unloaded pellets; iii) Powder coating of drug-loaded pellets. This research analyzed different combinations of polymer, plasticizer, co-plasticizer and other adjuvant by evaluating free films and their assessment through curing and storage. Then suitable coating formulations were utilized for the development of the manufacturing process upon placebo pellets. Subsequently, the dry powder coating process was successfully optimized to coat caffeine-loaded pellets.