A Simplified Model Structure for Compression Characterization of Pharmaceutical Tablets

Despite -or maybe because- many shortcomings, Heckel's equation is by far the most investigated compressibility model for decades. The somewhat overlooked Gurnham equation is proposed as a more stable and better fitting compressibility model. Combining this equation with a linear model for the strength/pressure relation provides a composite function identical with the often-used Ryshkewitch equation for the relation between strength and porosity. It is thus questioned whether the three-dimensional compression characterization presented in USP monograph <1062> is correct. Substantial errors in computed parameters are revealed with consequences for reproducibility or inter-lab assessments. Elastic recovery is proposed as a more interesting and relevant characteristic in relation to pharmaceutical tablet formulation.