Damage of the microcapsule wall during compression

Abstract

Cellulose acetate phthalate microcapsule containing phenacetin was used as a model and the effect of compression force and characteristics of excipients on the damage of microcapsule wall during compression process were studied. Calcium citrate with different particle sizes and microcrystalline cellulose were used as excipients. The degree of damage of the wall was evaluated from the dissolution rate of phenacetin and results observed by scanning electron microscopy. When calcium citrate was used as an excipient, microcapsule wall was damaged remarkably in the early stage of compression (P=100 kg/cm2), and the degree of damage was affected by particle size of calcium citrate. The larger particles caused more remarkable damage. In the case of microcrystalline cellulose which showed high compressibility, the degree of damage under high compression force (P=1000 kg/cm2) was less than that of calcium citrate under low compression force (P=100 kg/cm2). From these results, it was considered that the magnitude and distribution of shear stress on the wall were affected by particle size and compressibility of excipients and that the degree of damage of microcapsule wall was different between calcium citrate and microcrystalline cellulose.