Characterization and evaluation of the performance of different calcium and magnesium salts as excipients for direct compression

The performance of a series of inorganic salts as direct compression excipients was systematically evaluated. The physical-chemical and technological properties of the different salts were investigated in terms of crystalline/amorphous state, morphology, granulometry, apparent/tapped density, specific surface area, flowability, compressibility, dilution and distribution coefficients. To achieve a comprehensive evaluation of the performance of the different salts, the data obtained by the various analyses were normalized, giving a score to each excipient for each evaluated property/parameter. Statistical elaboration (JMP software) of the full dataset provided a final ranking of the powders based on their effectiveness as direct compression excipients. The salt emerged as the best was used to prepare direct-compression tablets, using cefixime as model drug, by modifying the composition of marketed tablets. A significant improvement of the mechanical properties of the new tablets was observed, compared to the marketed ones, with a crushing strength increase of over 30%, without variations of the drug dissolution profile. Even though the resulted ranking cannot have an absolute value, being the behavior of the different excipients susceptible to the kind of drug and other formulation excipients, the proposed approach can provide a useful model for a systematic evaluation and comparison of potentially similar excipients.