Water-solid interactions. IV. Influence of moisture sorption on the compaction of film-coated particles

The effect of moisture sorption on the compaction properties of model modified-release (MR) pellets coated with ethyl cellulose/hydroxypropylcellulose film has been studied for the MR pellets alone and in binary mixtures with microcrystalline cellulose, lactose alpha-monohydrate, or lactose 9% amorphous. The in vitro dissolution rate prior to and after compaction was used as an indirect method of evaluating the effect of exposing the MR pellets to a compaction force. Moisture sorption as well as the glass transition temperature (Tg) using differential scanning calorimetry (DSC) were determined as a function of humidity for cast film conditioned at different humidities using a climate test chamber. The compaction properties of lactose and microcrystalline cellulose were altered by the addition of MR pellets, resulting in a robust tablet mass and a tensile strength of the tablet masses that was less sensitive to moisture. The amount of moisture sorbed was found to have little influence on the formation of cracks or on the rupturing of film-coated MR pellets during compaction. This was probably a result of both the small depression in the Tg for the film system at increasing RH and the robustness of the film chosen. The results also showed that the volume reduction properties of the tableting excipients were of importance for reducing damage to the film coating. Lactose had a higher protective effect on the film-coated MR pellets compared to microcrystalline cellulose.