nonproprietary names are not subject to proprietary trademark rights but are entirely in the public domain. This distinguishes them from the trademarked names that have been registered for private use. Name assignment Assignment of a USAN takes into account practical considerations, such as the existence of trademarks, international harmonization of drug nomenclature, the development of new classes of drugs, and the fact that the intended uses of substances for which names are being selected may change. USANs assigned today reflect both present nomenclature practices and older methods used to name drug entities. Early drug nomenclature was based on the chemical structure. As newer drugs became chemically more complex and numerous, nonproprietary names based on chemistry became long and difficult to spell, pronounce, or remember. Additionally, chemically derived names provided little useful information to non-chemist health practitioners. Considering the needs of health professionals led to a system in which USANs reflect relationships between new entities and older drugs, and avoid names that might suggest non-existent relationships. Current nomenclature practices involve the adoption of standardized syllables called "stems" that relate new chemical entities to existing drug families. Stems may be prefixes, suffixes, or infixes in the nonproprietary name. Each stem can emphasize a specific chemical structure type, a pharmacologic property, or a combination of these attributes. The recommended list of USAN stems is updated regularly to keep pace to accommodate drugs with new chemical and pharmacologic properties. As a general rule, the application for a USAN should be forwarded to the USAN Council after the Investigational New Drug (IND) is active and clinical trials have begun. Many drug manufacturers seeking a USAN are multinational companies with subsidiaries in various parts of the world or contractual agreements with drug firms outside the United States. Therefore, it is highly desirable to the pharmaceutical company, the various nomenclature committees, and the medical community in general that a global name be established for each new single-entity compound introduced. Assigning a USAN and standardizing names internationally can take anywhere from several months to a few years. Differences between USAN and INN Examples of drugs for which the USAN differs from the INN include: See also British Approved Name International Nonproprietary Name Nomenclature of monoclonal antibodies United States Pharmacopeia References External links US Adopted Names Program Pharmacological classification systems Names