Effects of the diluent type on compressional characteristics of the mixed stem bark extract of Anogeissus leiocarpus and Prosopis africana tablet formulation.

The hot water extract of a mixture of stem barks of Anogeissus leiocarpus and Prosopis africana was formulated into tablets using the wet granulation method of massing and screening. The Heckel equation was used to study the compaction characteristics of the extract formulated with lactose (water-soluble) or magnesium carbonate (water-insoluble) as diluents. Granules prepared using magnesium carbonate were found to exhibit two stages of deformation - an initial fragmentation followed by plastic flow while those formulated with lactose consolidated mainly by plastic deformation. Compressibility profiles of the formulations were affected by the diluent type. Tensile strength of granules formulated with magnesium carbonate was found to increase as the compression pressure increased from 56.6 to 113.2 MN m(-2) while the tensile strength of tablets formulated with lactose had its maximum at a compression force of 84.9 MN m(-2).