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The effects of selected superdisintegrants on the dissolution behavior of several cationic drugs with varying water solubility were evaluated. All formulations were made with fixed disintegrant concentration and equal drug load using a model formulation. Tablets were made by direct compression and were compressed to equal hardness. Dissolution studies were carried out in dissolution media specified in the compendium (USP) or in media recommended by the U.S. Food and Drug Administration (FDA) for the respective actives. The effect of media pH on the dissolution of drugs was also evaluated.The use of crospovidone significantly improved the dissolution of the cationic drugs in the model formulation when compared with the other superdisintegrants studied. The compendial or the FDA recommended media, in most cases, was able to discriminate among the tablets containing different superdisintegrants.Crospovidone can be effectively used as a tablet disintegrant to improve the dissolution of either soluble or poorly soluble cationic drugs.

Metformin microspheres with sodium alginate alone and in combination with gellan were prepared using an emulsion-cross linking method. The prepared microspheres were evaluated for their physico-chemical characteristics like particle size, morphology using SEM, incorporation efficiency, equilibrium water content (swelling) and in vitro drug release. The effect of various formulation variables like polymer concentration (sodium alginate; and proportion of gellan in microspheres prepared by a combination of sodium alginate and gellan), drug loading, crosslinking agent concentration and cross-linking time on the in vitro dissolution of the prepared microspheres were evaluated. The results showed that both the particle size and the incorporation efficiency were proportional to the polymer concentration. In case of microspheres containing both sodium alginate and gellan, the mean diameter and the incorporation efficiency were higher than the corresponding microspheres containing only alginate, both increasing with an increase in proportion of gellan. The prepared microspheres were found to be discrete and spherical in shape and were successful in sustaining the drug release for 8 hours. Incorporation of gellan caused a significant decrease in drug release. The release followed a biphasic profile, in all cases, characterized by an initial phase of moderate drug release followed by a phase of higher release. Further, the kinetic treatment of the dissolution data revealed the prevalence of matrix diffusion kinetics.

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