The new practice of using water activity as a tool for establishing the BUD of a CNSP is described in Section 10.3 of the to-be-official USP <795> chapter. Water activity testing in accordance with USP <922> is not required but is highly recommended to support the established BUD of the CNSP. Water activity testing should be considered in cases where there is an absence of a USP-NF Compounded Preparation Monograph and/or CNSP-specific stability information.
