Nonproprietary Names - AMA Manual of Style

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Nonproprietary Names 


Margaret A. Winker

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Nonproprietary Names


The INN reflects the chemistry, pharmacologic action, and therapeutic use through its stem. Herbals (see 15.4.15, Herbals and Dietary Supplements), homeopathic products, mixtures, drugs in common use for decades (eg, morphine, codeine), and those with trivial chemical names (eg, acetic acid) do not receive INNs. The committees involved in reviewing and selecting INNs agree to a name that is then published as a proposed INN. During a 4-month comment period, any person can comment on or object to the proposed INN. If no objection is raised, the name is published as a recommended INN. New INNs are published in WHO Drug Information in English, French, and Spanish ( A cumulative INN list is published, which also includes INNs in Russian. More than 7000 INNs have been designated as of 2004; 120 to 150 are added each year.2


In addition to having a distinct sound and spelling to avoid confusion with other names, the INN includes a “stem” that designates the drug as a member of a family of related drugs, indicating that the drug has similar pharmacologic properties.2

The stem is usually a suffix common to a particular drug class that is incorporated into new drug names to indicate a chemical and/or pharmacologic relationship to older drugs.7 For example:

H2-receptor antagonists: cimetidine, ranitidine, lupitidine (-tidine is the stem)

Tyrosine kinase inhibitors: canertinib, imatinib, mubritinib (-tinib is the stem)

β-Blockers: propranolol, timolol, atenolol (-olol is the stem)

Combined α- and β-blockers: labetalol, medroxalol (-alol is the stem)

For some classes of drugs, the position of the stem varies within the drug name. For the group of antiviral drugs (not necessarily having common pharmacologic properties), the stem may be vir-, -vir-, or -vir:

ganciclovir, enviradene, viroxime, alvircept, delavirdine

Approved stems are provided on the USAN website7 and in the USP Dictionary.1(pp1226-1232)

The goal of the WHO INN system is to have a single INN for each drug used throughout the world. However, if the substance was in existence before the coordination of nomenclature by WHO, nonproprietary names may differ between countries. For example, acetaminophen is the USAN for the same drug that has the BAN and DCF name paracetamol. The USAN albuterol has a JAN of salbutamol (not to be confused with salmeterol, a longer-acting β-adrenergic agonist).1(p44) Some other names are more similar, such as cyclobarbitone (BAN) and cyclobarbitol (USAN). For these few drugs for which nonproprietary names differ by country, the nonproprietary name used depends on the primary audience, although the European Union has required that nonproprietary names that differ from the INN will be phased out over time. In cases in which international recognition is essential (such as adverse drug reactions), both names should be given at first mention.

Acetaminophen (paracetamol) was recommended as an initial treatment for pain in the practice guidelines.

The existence of more than 1 nonproprietary name is also important when performing searches on drugs in journals or databases; all nonproprietary names for a particular drug should be used for a complete search. The USP Dictionary1 lists the INN and nonproprietary names by nomenclature agency, if they differ.

Orphan Drugs.

Drugs that may be used to treat relatively rare diseases but that otherwise are believed to have limited marketability are termed orphan drugs.8 When a drug is designated an orphan drug by the FDA, the name it receives is not necessarily the name it will receive if it is approved for marketing.1(p13) A listing of orphan drugs is available at

Changes in Nonproprietary Names.

Nonproprietary names may be changed if they are believed to be confusing or could result in medication errors, or if they are proven to infringe on trademark. For example, the antineoplastic compound mithramycin became plicamycin to avoid confusing mithramycin with the similar-sounding antineoplastic mitomycin and its proprietary name Mutamycin. The nomenclature committees have procedures for applying to change the nonproprietary name. (USAN’s procedure is available at

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