Use of the sorption-desorption moisture transfer model to assess the utility of a desiccant in a solid product

Abstract

Desiccants are frequently included in moisture-sensitive solid pharmaceutical products to scavenge moisture in the package and prevent this water from interacting with the product. This study has demonstrated the utility of the sorption-desorption moisture transfer (SDMT) model for predicting moisture transfer between an aspirin formulation and a silica/carbon desiccant for defined masses of each component and their initial moisture contents. Furthermore, simulations were conducted that accounted for permeation of moisture into the container for three markedly different masses of formulation that correspond to 1, 75, and 1500 tablets with 0–2 g of desiccant. For this formulation/ desiccant system, desiccant clearly had a marked effect in reducing the relative humidity inside the container for a significant time period for the single tablet and 75 tablet cases. However, the desiccant exhibited no practical effect in reducing relative humidity inside the container compared to formulation without desiccant for the 1500 tablet case. In conclusion, the SDMT model can account for the permeation properties of the package, the initial masses and moisture contents of the formulation and desiccant, and the total moisture sorption capacity of the formulation and desiccant to predict whether a desiccant will offer a significant moisture protective (i.e., reduced relative humidity inside the package) effect for a defined product.