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Updates to Chemical Information Section

Type of Posting: General Announcement

Posting Date: 27–Dec–2013

The purpose of this notice is to provide a detailed overview on updates to the Chemical Information section in USP–NF monographs. This explanation will also be included in the Mission and Preface beginning with the First Supplement to USP 37–NF 32.

Updates to the Chemical Information section at the beginning of monographs occur on an ongoing basis and are not identified with revision symbols. Chemical names and molecular weights are updated when a monograph undergoes revision to match the official source, USAN. Chemical structures are updated on a continuous basis.

Chemical names typically reflect the naming conventions at the time of the monograph development or revision. If the nomenclature rules of CAS or IUPAC are significantly changed, the chemical names can be revised or added to implement those rules. Molecular weights are derived from the chemical formula and are based on the table of atomic weights. Atomic weights are recommended by the IUPAC and reflect the isotopic composition of normal terrestrial material. When the IUPAC recommended values are changed, it is understood that the changes in molecular weights will be made in due course.

Graphical representation of the chemical compound structures is intended to help establish chemical identity and is understood to represent one of many possible ways to depict the molecule. Changes in the graphical representation resulting in the same chemical information, e.g., a flipped chiral molecule, may be introduced outside of the revision process. It is also understood that in the case of tautomerism, the molecule depicted may be one of the tautomers, but it is understood that it is intended to represent all isomers in equilibrium. Stereogenic centers depicted with plain bonds imply mixtures of pertinent stereomers—enantiomer, diastereomers, epimers (anomers), etc.

Depending on the timing of these updates, users may see a difference in a chemical structure between the publications in PF and USP–NF, and between the USP–NF print version and the online version.

Should you have comments or questions please contact Andrzej Wilk, Senior Scientific Liaison (301-816-8305 or