Effect of acrylic resins on the rheological and compressibility properties of paracetamol: formulation of directly compressible matrix systems

A phase separation technique allowed the poor flow properties and low compressibility of paracetamol to be changed, yielding a material, mo- dified paracetamol, with improved flow properties. Matrix tablets con- taining modified paracetamol with acrylic resins, Eudragit® E, L and S were prepared, with a 2% lubricant as the only excipient. Paracetamol was selected as a model drug. Tablets weighing 250 mg were prepared at the maximum compression force accepted by our formulations, using a typical eccentric machine with 10-mm punches. The influence of the type and proportion of Eudragit® and mean particle size on flow properties was investigated. The technological parameters and dissolution charac- teristics of the matrix tablets were also studied. The different beha- viour of the rheology of homogeneous and heterogeneous powder fractions was detected by means of correlation study of dynamic and static rheo- logical properties. The importance of surface and geometry characte- ristics of the powdered particles on flow properties was highlighted. The dissolution assay shows diffusion-controlled release from tablets containing Eudragit® L and S. An exponential relation between tensile strength and t 50 values was found for Eudragit® S tablets