Characterization of particle deformation during compression measured by confocal laser scanning microscopy

Direct compression of riboflavin sodium phosphate tablets was studied by co nfocal laser scanning microscopy (CLSM). The technique is non-invasive and generates three-dimensional (3D) images. Tablets of 1% riboflavin sodium ph osphate with two grades of microcrystalline cellulose (MCC) were individual ly compressed at compression forces of 1.0 and 26.8 kN. The behaviour and d eformation of drug particles on the upper and lower surfaces of the tablets were studied under compression forces. Even at the lower compression force , distinct recrystallized areas in the riboflavin sodium phosphate particle s were observed in both Avicel PH-101 and Avicel PH-102 tablets. At the hig her compression force, the recrystallization of riboflavin sodium phosphate was more extensive on the upper surface of the Avicel PH-102 tablet than t he Avicel PH-101 tablet. The plastic deformation properties of both MCC gra des reduced the fragmentation of riboflavin sodium phosphate particles. Whe n compressed with MCC, riboflavin sodium phosphate behaved as a plastic mat erial. The riboflavin sodium phosphate particles were more tightly bound on the upper surface of the tablet than on the lower surface, and this could also be clearly distinguished by CLSM. Drug deformation could not be visual ized by other techniques. Confocal laser scanning microscopy provides valua ble information on the internal mechanisms of direct compression of tablets . (C) 1999 Elsevier Science B.V. All rights reserved.