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Approved Stems

USAN Council statement on the use of new stems approved at the Jan. 26, 2007 meeting of the USAN Council

Recently, the USAN Council has been receiving an increasing number of requests for new stems. However, with hundreds of existing stems in the USAN nomenclature scheme, a stem that correctly and meaningfully describes a new substance usually exists.

The goal of the USAN Program is to provide meaningful, informative designations for compounds, enhancing correct prescribing practices and patient safety. Because excessive new stem creation diminishes the usefulness of the nomenclature system to health care practitioners, the USAN Council strives to use existing stems whenever possible. Thus, for a new stem to be assigned to a substance, the burden of proof falls on the applicant to demonstrate that it is warranted.

If, in the opinion of the USAN Council, substantial clinical and preclinical data show that a substance is unique and cannot fit into the existing nomenclature scheme, a new stem may be coined.

Using stems

The listing of USAN stems represents common stems for which chemical and/or pharmacologic parameters have been established. These stems and their definitions, approved by the USAN Council, are recommended for use in coining new nonproprietary names for drugs that belong to an established series of related agents.

USAN appropriately incorporates this established class stem system. By doing so, similar compounds maintain a common "family" name that provides immediate recognition.

The list is not exhaustive, in that it does not include all stems used by the Council and other national or international nomenclature groups. It is the nature of the nomenclature process that new, potential stems are constantly being created and that definitions of older stems may need to be modified as new information becomes available.

New stems
USAN stems that received official approval by the USAN Council at the July 12, 2013 USAN Council meeting.