Three small glass vials, each containing one tablet, are placed on a white surface. A device labeled

Water Activity Determination

Controlling water activity in oral solid dosage (OSD) product is essential to maintaining the potency, purity, and safety of drug product. With the publication of USP<922>, pharmaceutical manufacturers are implementing water activity measurements during formulation and packaging development phases and into the routine stability testing programs.

Determining water activity using headspace analysis is….

  • A direct measurement of water activity
  • Directly correlated to product stability
  • Not interfered with by other volatiles
  • Not influenced by "moisture memory" from other samples

As explained in the USP<922> general chapter, water activity (aw) is the amount of free or loosely bound water available to participate in unwanted chemical, physical and biological reactions. It is water activity, not total water content, that correlates to the critical quality attributes of tablets and capsules. Monitoring water activity throughout the product life cycle is important to control critical quality attributes such as microorganism growth, product degradation, product dissolution and product hardness or friability.

With non-destructive headspace analysis, the water activity of OSD products is readily determined, allowing the generation of robust science-based data on key product quality parameters.

A collection of various pill blister packs containing different types, shapes, and colors of tablets and capsules scattered on a white surface.

Is your primary package able to protect your product over shelf life?

Water activity determination is used to assess the level of protection provided by primary packaging for an oral solid dosage (OSD) product over its shelf life. Primary packaging must maintain a low relative humidity for as long as necessary to ensure the pharmaceutical product maintains its key quality attributes up to its expiration date. 

LIGHTHOUSE can aid in development studies to select the best possible package for your product .


Direct water activity measurements help determine product stability and quality

Direct water activity measurements can determine the impact of moisture on the potency and dissolution of a dry pharmaceutical product. This helps determine the stability and quality of these products. Moreover, it is crucial to gain insight into how temperature and humidity impact powder flow, compression, adhesion, and the physical characteristics of the tablet, pill, or capsule. Water activity is strongly correlated to all of  these critical factors and provides unique and critical information at each stage in the product life cycle.


Reduction of microbial growth by controlling water activity

Oral solid dosage (OSD) products are subject to microbiological examination prior to release and during stability testing. USP <1112> describes how water activity determination can be used to reduce the need for frequent microbial limit testing and screening. By controlling the water activity of a product, beginning with its raw materials, it is possible to greatly reduce, or even eliminate, the viability of microbial growth.