Compression of enteric-coated pellets to disintegrating tablets: uniformity of dosage units

Enteric-coated bisacodyl pellets were compressed into tablets using granules and powders as filler-binders of different particle size and cohesiveness. The effects on the uniformity of content and mass were investigated. The mixtures contained between 10 and 70% mass/mass pellets with a particle size in the range 0.8-1.25 mm. Egermann's equations were used to calculate the coefficients of random variation of content. Tablets containing 10% mass/mass pellets showed pronounced variations in mass and content. This was attributed to the large particle size of the pellets as compared with the tablet size, Mixtures with 30% mass/mass pellets showed good uniformity of mass and of content if additional granules were used as excipients. segregation occurred if only finer excipients were used. With 50-70% mass/mass pellets in a tablet, good content uniformity was found with all filler-binders used. This can be explained by the formation of a percolating cluster of the pellets, which prevented segregation. With 50% mass/mass, corresponding to 30% vol./vol., and more pellets in the mixture, the coefficient of variation of content agreed well with the values calculated according to Egermann's equations. (C) 1998 Elsevier Science S.A. All rights reserved.