In this paper, finite element methods are used to investigate the compaction process of pharmaceutical tablets. The pharmaceutical powder is treated as a continuum with its elastic-plastic constitutive behavior described by the Drucker-Prager Cap (DPC) model. The model captures the shearing and densification of the powder during compaction and predicts the localized stress and relative density distributions. The DPC model was implemented for a cylindrical tablet geometry using the commercial software, Abaqus, for micro-crystalline cellulose, with the material parameters taken from the literature. The elastic-plastic material parameters of the constitutive model are strongly dependent on the relative density of the powder and evolve during the tablet compaction process. In the current study, a modified material model is used in which the DPC parameters are dependent on the current relative density of the powder and, hence, provide more accurate macroscopic property distributions within the tablet. The results show that significant differences in the final tablet stress and relative density distributions occur when constant material properties and relative density dependent properties are used.