Effect of the compaction parameters on the final structure and properties of a press-coated tablet (Tab-in-Tab): Experimental and numerical study of the influence of core and shell dimensions

Abstract

With increasing interest in chronopharmaceutics, press-coated tablets have become a key technology in the field of modified release drug delivery systems. Although their benefits in terms of drug release have been largely studied, the comprehension of the compaction process of press-coated tablets is yet to complete. Particularly, the effects of geometrical parameters like the ratios between the thickness/diameter of the core and the thickness/diameter of the whole tablet were so far not much considered. Moreover, there is only few studies in the literature about the effect of the press-coating compression on the final structure and properties of the core. The present work consists in a joint experimental and numerical study that aims to assess these points. The study revealed high stress concentrations on the core during compression, causing high permanent deformations of the core, especially when the ratio between the core thickness and the total tablet thickness was high. The mechanical properties of the core tablet were also shown to be impacted: its density and strength were found to decrease before increasing again along the coating-compression. This effect was highlighted to be dependent on the triaxiality of the stress state (i.e. the ratio between the stresses in the different directions), itself depending on the two studied geometrical parameters. As the properties of the core affect the release attributes, ratios between the dimensions of the core and the dimensions of the whole tablet (thickness, diameter) should be taken into account as critical parameters for the manufacture of press-coated tablets.