Ann Newman - "Minireview: Characterization of the "'Hygroscopic"'  Properties of Active Pharmaceutical Ingredients"  A. W. Newman, S. M. Reutzel-Edens, G. Zografi

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      Publication Details (including relevant citation   information):

      J. Pharm. Sci., 2008, 97(3), 1047-1059.


      The amount of water vapor taken up by an active pharmaceutical   ingredient (API) as a function of relative humidity is routinely   evaluated to characterize and monitor its hygroscopicity  throughout the drug development process. In this minireview we   address the necessity of going beyond the measurement of water   vapor sorption isotherms to establish the various mechanisms by   which solids interact with water and the important role played by   the crystalline or amorphous form of the solid. Practical   approaches for choosing experimental conditions under which water   vapor sorption should be measured, including the pre-treatment of   samples and the time allowed to reach an equilibrium state are   presented. With the assistance of a flowchart, we provide a basis   for the systematic examination of samples to establish the likely   mechanisms of sorption and the indicators pointing toward future   problems with physical and chemical instabilities. Finally, we   present strategies for managing materials that might be   susceptible to the detrimental effects of water vapor sorption.

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