Moisture-sensitive products, stability study

The storage conditions and the length of the studies should be sufficient to cover storage, shipment, and subsequent use. Both drug substances and products should be evaluated under storage conditions that test for thermal stability (temperature effect) and moisture sensitivity (humidity tolerance). 

Badway, S. I. F., Gawronski, A. J., and Alvarez, F. J. (2001), Application of sorption-desorption moisture transfer modeling to the study of chemical stability of a moisture sensitive drug product in different packaging configurations, Int. J. Pharm., 223(1-2), 1-13. 

Sensitivity to moisture or potential for solvent loss is not a concern for drug products packaged in impermeable containers that provide a permanent barrier to passage of moisture or solvent. Thus, stability studies for products stored in impermeable containers can be conducted under any controlled or ambient humidity condition. 

Heat and humidity are often combined to determine the sensitivity of the API and product, packaged and unpackaged, to these stress conditions. For example studies at 40°C/75% RH and at 50 or 60°C are typically part of a stability program and can also be used to facilitate method specificity studies. Pre-formulation compatibility studies in which the API is combined with various excipients with and without moisture addition and stored at stress conditions may also be helpful in establishing forced degradation conditions for studying method specificity. 

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