Several questions have been raised concerning the impact of "United States Pharmacopeia (USP) <922> Water Activity" on pharmacy compounding.

Most are already aware of "USP Chapter <1112> Application of Water Activity Determination to Nonsterile Pharmaceutical Products" whose purpose is to provide a tool and rationale for reducing the frequency of microbial limit-testing and screening for objectionable microorganisms for product release and stability testing methods contained in

• "USP Chapter <61> Microbial Enumeration Tests" and
• "USP Chapter <62> Tests for Specified Microorganisms".

It is quite clear that those chapters are concerned with microbial limit tests, but what about "USP <922> Water Activity"?

"USP <922> Water Activity" is intended to provide guidance for performing measurements of water activity. The chapter provides methods for:

• Qualification of instruments,
• Calibration of instruments,
• Methods for performing water activity measurements, and
• Reporting of results.

In other words, this chapter outlines the recommended methods to qualify, calibrate, and use water activity meters to accurately measure the water activity of raw materials and products.

The General Outline of the chapter includes:

• Introduction
• Background
• Application of Water Activity Measurements
• Types of Water Activity Meters
• Operation and Calibration of Water Activity Meters
• Assay Verification and Validation
• Troubleshooting
• Glossary
• References

It is quite clear that the primary target of this Chapter is for those facilities/laboratories actually conducting water activity measurements. A copy of the notice can be obtained at:

https://www.uspnf.com/notices/922-water-activity

Loyd V. Allen, Jr., PhD, RPh
Editor-in-Chief
IJPC
Remington: The Science and Practice of Pharmacy Twenty-second edition