Guidelines released on USAN naming

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The American Medical Association (AMA) has issued guidelines on naming using United States Adopted Names (USAN), which are unique non-proprietary names assigned to pharmaceuticals sold in the US.


Non-proprietary names are names for products that are not subject to trademark rights. The International Nonproprietary Name (INN) is the official generic, non-proprietary name given to a pharmaceutical, such as paracetamol.

In the US, there is also the USAN, an additional non-proprietary name selected by a council to ensure ‘safety, consistency and logic’. The USAN programme has named over 150 drugs each year in recent years.

Drug names in the US consist of three parts:
         Prefix: Has no meaning; differentiates drug from others in class

         Infix:  Used occasionally; further subclassifies

         Stem: Indicates place in nomenclature scheme; drugs with the same stem are related.
                     The stem is typically at the end of the drug name and a new stem suggests a new mechanism of action.

The recently released guidelines provide nine ‘guiding principles’ on naming, summarized here:
        1. A non-proprietary name should be useful to healthcare practitioners. This means the name should be suitable for:
                 a. use in routine prescribing, ordering, dispensing and administering drugs
                 b. use in educational programmes and in scientific and lay publications
                 c. international use
        2. Simplicity, euphony (ease of pronunciation) and ease of recognition and recall contribute to usefulness, for example:
                 a. the name of the active ingredient of a drug should be a single word, preferably of less than four syllables
        3. A drug name should reflect characteristics/relationships of practical value
                 a. A common, simple world element (known as a stem) should be included in the names of all members of a group of
                     related drugs with common characteristics
                 b. Distinctive terminology should be used for specific drugs, e.g. epoetin alfa and epoetin beta
        4. A name should not conflict or be confused with other non-proprietary names or trademarks
        5. Names with established usage are preferred
        6. Where possible, substances should be assigned to existing stems describe the substance, its action or use
        7. Identical negotiations submitted by two or more manufacturers will be conducted in accordance with the USAN Council's
            confidentiality practices
        8. A USAN request should be made only after the drug sponsor has submitted an Investigational New Drug (IND)
            Application to the Food and Drug Administration (FDA) 
        9. Negotiations can be placed on hold upon request of the manufacturer

The guidelines provide a number of examples of USAN names, including the stem -stat for cholesterol treatments, e.g. atorvastatin calcium, rosuvastatin; the stem -prazole for heartburn treatments, e.g. esomeprazole magnesium, lansoprazole; and -oxetine for antidepressants with a chemical structure related to fluoxetine, e.g. duloxetine hydrochloride.

The guidelines close with a number of nomenclature rules, such as not using prefixes which imply that a drug is newer or more effective or prefixes that refer to a Latin or Greek number.

The release of the guidelines comes amidst changes to the naming of biological drugs in the US, which propose assigning a non-proprietary name for biologicals that include an ‘FDA-designated suffix’ [1] and have come under some criticism [2].

Related articles
Distinct suffixes will aid biosimilar competition, says new research

Health Canada announces naming convention for biologicals

1. GaBI Online - Generics and Biosimilars Initiative. FDA proposes update to biosimilar naming guideline []. Mol, Belgium: Pro Pharma Communications International; [cited 2020 Apr 10]. Available from:
2. GaBI Online - Generics and Biosimilars Initiative. Stakeholders question FDA’s guidance on naming biologicals []. Mol, Belgium: Pro Pharma Communications International; [cited 2020 Apr 10]. Available from:

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Source: AMA

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