A Simplified Model Structure for Compression Characterization of Pharmaceutical Tablets.

Despite, or maybe because of, 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.