Impact of Amylose-Amylopectin Ratio of Starches on the Mechanical Strength and Stability of Acetylsalicylic Acid Tablets.

The two main components of starch - amylose and amylopectin, are responsible for its interaction with moisture. This study investigated how moisture sorption properties of the starches with different amylose-amylopectin ratio impacted tablet properties including drug stability. The starch samples were equilibrated to 33, 53, and 75% relative humidity (RH) and then assessed for tabletability, compactibility, and yield pressure. Effect of humidity on viscoelastic recovery was also evaluated. Tabletability and compactibility of high-amylose starch were better than that of high-amylopectin starch at 33 and 53% RH. However, at 75% RH, the reverse was observed. In terms of yield pressure, high-amylose starch had lower yield pressure than high-amylopectin starch. High-amylose starch tablets also exhibited lower extent of viscoelastic recovery than high-amylopectin starch tablets. The variations in the tableting properties were found to be related to relative locality of the sorbed moisture. Degradation of acetylsalicylic acid in high-amylose starch tablets at 75% RH, 40°C was less than the tablets with high-amylopectin starch. This observation could be attributed to the greater amount of water molecules binding sites in high-amylose starch. Furthermore, most of the sorbed moisture of high-amylose starch was internally absorbed moisture, therefore limiting the availability of diffusible sorbed moisture for degradation reaction. Findings from this study could provide better insights on the influence of amylose-amylopectin ratio on tableting properties and stability of moisture-sensitive drugs. This is of particular importance as starch is a common excipient in solid dosage forms.