BRIEFING

 Colistimethate Sodium. This proposal is based on the version of the monograph official as of May 1, 2020. The proposal in PF 49(1) [Jan.–Mar. 2023] has been canceled and is being replaced with a new proposal. This new proposal contains modifications made on the basis of public comments. The following changes are proposed:

1. Update the chemical structure and chemical information to align with the compound and the current USP format.

2. Add information to the Definition.

3. Add the Identification B and Identification C tests.

4. Add an Organic Impurities test with a liquid chromatographic procedure. The procedure was validated using the Acquity UPLC CSH C18 brand of column with L1 packing. The typical retention time for colistimethate AS6 is about 13 min.

5. Revise the pH and Free Colistin tests to align with the actual practice.

6. Add a Composition test with the same liquid chromatographic procedure as in the test for Organic Impurities.

7. Update the USP Reference Standards section.

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

 (BIO4: J. Zhang)

 Correspondence Number—C326195