This study consists of two experimental designs. Within the first one, suitable technique for application of model drug onto inactive pellets was evaluated and formulation and process parameters with greatest impact to process efficency and useful yield were determined. Results of experiments showed that formulation characteristics were the ones with the greatest impact on coating efficiency and that suspension layering technique was signifficantly better for drug application onto inactive pellets in comparison to solution layering during which pronounced agglomeration of pellets occurred. Analysis of drug-polymer interactions by differential scanning calorimetry was performed to explain the results of experiments. The reason for agglomeration of pellets during solution layering was formation of low Tg amorphous form of model drug.

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