Vacuum Rotary Kiln Drying of Aspirin Tablets and Acetaminophen Wet Granules under Reduced Pressure

Pharmaceutical solid dosage forms necessitate long-term stability, which can be effectively achieved by removing excess residual water from the final products. To enhance the drying process in pharmaceutical manufacturing, we propose a new method: vacuum rotary kiln drying. This method allows for drying at low temperatures and imposes minimal mechanical restrictions on dosage forms. This report examines the drying of aspirin tablets and acetaminophen granules, aiming to improve the stability of moisture-sensitive drugs and apply the method to wet granulation processes. Aspirin tablets dried in a vacuum rotary kiln within a few hours showed no degradation, even after 3 months of storage. The physical properties of acetaminophen granules dried using this method and the tablets produced from them were comparable to those obtained using fluidized bed drying or tray drying. We conclude that vacuum rotary kiln drying is applicable to pharmaceutical manufacturing, with potential benefits including improved drug stability and reduced drying time.