The USAN Council’s goal is to provide meaningful designations for compounds, enhancing prescribing and patient safety. Excessive stem creation diminishes the usefulness of the system. Therefore, the council strives to use existing stems whenever possible. For a new stem to be assigned, the burden of proof falls on the applicant to show it is warranted. If, in the opinion of the council, substantial data shows a substance is unique and cannot fit existing nomenclature, a new stem may be coined.
The listing of USAN stems (XLSX) represents common stems for which chemical and/or pharmacologic parameters have been established. These Council-approved stems and their definitions are recommended for use in coining new nonproprietary drug names belonging to an established series of related agents.