Pellet-containing tablets - Examination of distribution and deformation behaviour

The distribution and deformation of enteric coated bisacodyl pellets in tab lets comprising of 70% of pellets and either 30% Avicel PH 101 or coarse Av icel granules, was investigated with respect to pellet damage using image a nalysis, scanning electron microscopy, compression analysis and dissolution assays. Use of coarse Avicel granules led to more marked deformation of pe llets within the tablet than with Avicel PH 101, as shown by SEM photograph s and a new fragmentation quotient derived from Heckel plots, tapped and bu lk density. Although less deformation occurred using Avicel PH 101, these t ablets released much more bisacodyl after 2 h in simulated gastric fluid th an pellets compressed with Avicel granules. Thus the decisive damage occurr ed not within the tablet matrix (even at a high degree of deformation), but at the surface of tablets, which was corroborated by a higher proportion o f deformed pellets on the tablet surface.