BRIEFING

 Mercaptopurine. This proposal is based on the version of the monograph official as of September 1, 2021. On the basis of the supporting data, it is proposed to revise the monograph with the following changes:

1. In the test for Organic Impurities:

   • Add a molecular weight conversion to the calculation formula to convert the relative response factor from against mercaptopurine anhydrous to against mercaptopurine monohydrate based on the original validation data received from an FDA-approved manufacturer.

   • Add a table and Note to the System suitability section to present relative retention times as an aid in peak assignment.

   • Revise the table in the Acceptance criteria to list only the limits for specified impurities, any unspecified impurity, and total impurities.

   • Under the Acceptance criteria, the numerical reporting threshold has been replaced with a reference to general chapter User-Determined Reporting Thresholds 〈477〉 for user flexibility. For more information about this change, please see the USP Compendial Notice “New Chapter 〈477〉 User-Determined Reporting Thresholds and its Implementation in USP−NF Monographs”.

2. Revise the Standard phosphate solution preparation in the test for Phosphorous for clarity.

 Additionally, minor editorial changes have been made to update the monograph to current USP style.

 (SM3: A. Leeks, Jr.)

 Case ID—SUB-1305