Physicochemical and mechanical properties of tablets are largely dictated by formulation compositions. Different excipients possess different tableting and moisture sorption behaviors. Therefore, this study was designed to elucidate the relative influence of the proportion of components in formulations on tablet properties. Acetylsalicylic acid (ASA) tablets containing different proportions of starch, microcrystalline cellulose (MCC) and calcium hydrogen phosphate dihydrate (DCP) were prepared. The excipients were evaluated for their moisture sorption properties. Mechanical strength of the tablets was determined alongside with ASA stability, by storing the tablets at 75% RH, 25 °C. The stability study showed the importance of drug loading level on its stability. For a fixed ASA proportion, formulations with more starch were able to absorb more moisture and possessed larger areas of hysteresis loop in their moisture sorption isotherms. The presence of starch contributed positively to ASA stability although increasing proportions of starch compromised the tablet mechanical properties. Contrastingly, MCC produced mechanically stronger tablets as its plastically deforming and fibrous properties contributed to a good structural network. The findings provide a deeper understanding of the dichotomous effect by the proportion of components in formulations containing a moisture sensitive drug on drug stability and mechanical strength of the resultant tablets.
Keywords: Drug stability; Excipients; Mixture design; Moisture; Tablet; Tensile strength.
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