By Michael Lally, Application and Validation Specialist, Lighthouse Instruments
The draft of the new general chapter USP <922> states that water activity determination can be used to assess the level of protection provided by primary packaging for an oral solid dosage (OSD) product over its entire 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 including potency, purity, dissolution rate, tablet hardness, and capsule swelling, up to its expiration date. During the development phase, data must be acquired to determine if an existing package can provide adequate protection, or if new technologies are required for new formulations. For commercial products, a replacement package must be assessed to determine if it has equivalent, inferior, or superior performance. Water activity (Aw) measurements provide unique information, and therefore expand and complement the data collected from USP<670> Auxiliary Packing Components and USP<671> Containers - Performance Testing.