# International nonproprietary name
An **international nonproprietary name (INN)** is a unique, globally recognized name in the public domain that identifies a pharmaceutical substance or active pharmaceutical ingredient; a nonproprietary name is also known as a generic name.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) The system is run by the World Health Organization (WHO), which collaborates with INN experts and national nomenclature committees to select a single name of worldwide acceptability for each active substance marketed as a pharmaceutical.[2](https://www.who.int/teams/health-product-and-policy-standards/inn/)
| Key fact | Detail |
|---|---|
| Definition | A unique, globally recognized, public-property name for a pharmaceutical substance; also called a generic name[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) |
| Origin | Initiated in 1950 by World Health Assembly resolution WHA3.11; began operating in 1953 with the first published list[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) |
| Scale | Cumulative list of some 9,300 names, growing by about 160 new INNs per year[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) |
| Governing rules | WHO Executive Board resolution EB15.R7, as amended by resolution EB115.R4[3](https://extranet.who.int/soinn/mod/glossary/showentry.php?eid=7) |
| Publication stages | Proposed INN, followed by a four-month objection period, then Recommended INN[4](https://www.who.int/publications/m/item/protection-of-inn-ensuring-patients--safety-and-intellectual-property) |
| Stem system | A common syllable, in most cases a suffix, marks pharmacologically related substances[3](https://extranet.who.int/soinn/mod/glossary/showentry.php?eid=7) |
| Relation to national names | British Approved Names (BAN), Dénominations Communes Françaises (DCF), Japanese Adopted Names (JAN), and United States Adopted Names (USAN) are, with rare exceptions, identical to the INN[2](https://www.who.int/teams/health-product-and-policy-standards/inn/) |
## Purpose and legal status
INNs exist so that health professionals have a unique, universally available name for each pharmaceutical substance, supporting clear identification, prescription, and dispensing of medicines and communication among professionals and scientists worldwide.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) To make the names universally available, WHO formally places them in the public domain, which is the basis of the designation "nonproprietary"; they can be used without restriction to identify pharmaceutical substances.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true)
Nonproprietary names are intended for use in pharmacopoeias, labeling, product information, advertising and other promotional material, drug regulation, and scientific literature, and as a basis for product names such as those of generics. Their use is normally required by national legislation or, as in the case of the European Community, by international legislation.[2](https://www.who.int/teams/health-product-and-policy-standards/inn/) WHO's authority rests on a constitutional mandate to "develop, establish and promote international standards with respect to biological, pharmaceutical and similar products".[2](https://www.who.int/teams/health-product-and-policy-standards/inn/)
## Selection procedure
INNs are selected by WHO's Expert Advisory Panel on the International Pharmacopoeia and Pharmaceutical Preparations serving the INN Expert Group, following a strict procedure carried out in close collaboration with national drug nomenclature bodies.[4](https://www.who.int/publications/m/item/protection-of-inn-ensuring-patients--safety-and-intellectual-property) The procedure and the General Principles for guidance in devising INNs were approved by the WHO Executive Board in resolution EB15.R7, as amended by resolution EB115.R4.[5](https://www.who.int/publications/i/item/9789240099388)
Names must be distinctive in sound and spelling and not liable to confusion with other names in common use.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) A new name is first published as a **Proposed INN**, and a four-month review period follows, during which any interested person can submit an objection; this protects trademark owners and ensures the name is safe for use as a medicine. A name is not published as an official **Recommended INN** while an objection is maintained.[4](https://www.who.int/publications/m/item/protection-of-inn-ensuring-patients--safety-and-intellectual-property)
## The stem system
A second defining feature of the system is that names of pharmacologically related substances demonstrate their relationship through a common "stem". Under resolution EB15.R7 as amended, "a group relationship of pharmacologically related substances should, if possible, be shown in the name by using a common stem." A stem is a syllable, or two to three syllables, inserted into the new INN, in most cases as a suffix, to indicate the pharmacological relationship.[3](https://extranet.who.int/soinn/mod/glossary/showentry.php?eid=7) A practitioner seeing the stem can recognize that a substance belongs to a group with similar pharmacological activity.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true)
**Examples of stems.** All iodine-containing contrast media carry the prefix io-, while β-adrenoceptor antagonists share a suffix.[1](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true) Most chemical substance classes are identified by a stem alone, but some stems contain infixes: -ast means "anti-allergic or anti-inflammatory, not acting as anti-histaminics" (as in -lukast, -milast, and -tegrast), -tinib denotes tyrosine kinase inhibitors (as in -brutinib, -citinib, and -metinib), and vir appears in antivirals (as in -asvir, -ciclovir, and -previr).[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC9122354/) A patient-facing example is montelukast, a leukotriene receptor antagonist for asthma, whose -lukast ending is shared by other drugs with similar pharmacological actions.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC13002644/)
The stem reference work, *Use of stems in the selection of International Nonproprietary Names (INN) for pharmaceutical substances*, is updated periodically; the 2024 edition runs to 242 pages and lists all proposed INN published in Lists 1 through 129 that contain stems, together with a classification system in which each category of pharmaceutical activity carries a code of a capital letter and three digits.[5](https://www.who.int/publications/i/item/9789240099388)
## Biologicals and evolving schemes
Naming biological substances presents particular difficulties because of their structural complexity, and the INN Programme has developed separate approaches, including one-word and two-word naming schemes, for different categories of biologicals.[8](https://www.sciencedirect.com/science/article/pii/S104510561930048X) Since the monoclonal antibody scheme was introduced, all pharmacological substances containing an immunoglobulin variable domain were coined with the stem -mab, and guidance has confirmed that -mab should be retained, including for antibody fragments.[6](https://pmc.ncbi.nlm.nih.gov/articles/PMC9122354/) • [9](https://www.who.int/publications/i/item/inn-07-215) In May 2022 WHO published a new monoclonal antibody nomenclature scheme in which the suffix -tug is used for monospecific full-length immunoglobulins with unmodified constant regions.[2](https://www.who.int/teams/health-product-and-policy-standards/inn/) Separate nomenclature schemes also exist for gene therapy substances and for cell therapies, the latter approved during the 63rd INN Consultation in 2016.[5](https://www.who.int/publications/i/item/9789240099388) • [10](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/nomenclature-schemes-advanced-therapies-201707.pdf)
## Relationship with trademarks and national names
INN and trademarks represent opposite concepts, but both define and distinguish a single product or substance: the INN identifies a medicinal substance, while brand names are linked to specific products owned by a single commercial entity.[4](https://www.who.int/publications/m/item/protection-of-inn-ensuring-patients--safety-and-intellectual-property) To avoid confusion that could jeopardize patient safety, trademarks should neither be derived from INNs nor contain common stems used in INNs.[2](https://www.who.int/teams/health-product-and-policy-standards/inn/)
Because of long collaboration between WHO and national bodies, national nonproprietary names such as BAN, DCF, JAN, and USAN are nowadays, with rare exceptions, identical to the INN.[2](https://www.who.int/teams/health-product-and-policy-standards/inn/)
## Use in pharmacovigilance
The stem system has a practical role beyond naming. Because drugs sharing a therapeutic target, substructure, or biochemical pathway often show similar adverse-effect profiles, known as class effects, stems, especially modern stems that are for the most part based on mechanism of action, serve as a structured basis for signal detection in pharmacovigilance.[7](https://pmc.ncbi.nlm.nih.gov/articles/PMC13002644/)
## References
1. [Guidance on the use of International Nonproprietary Names (INNs) for pharmaceutical substances, WHO](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/who-pharm-s-nom-1570.pdf?download=true)
2. [International Nonproprietary Names Programme and Classification of Medical Products, WHO](https://www.who.int/teams/health-product-and-policy-standards/inn/)
3. [What is an INN stem? SoINN glossary, WHO](https://extranet.who.int/soinn/mod/glossary/showentry.php?eid=7)
4. [Protection of INN ensuring patients' safety and intellectual property, WHO Drug Information Vol. 37, No. 2, 2023](https://www.who.int/publications/m/item/protection-of-inn-ensuring-patients--safety-and-intellectual-property)
5. [Use of stems in the selection of International Nonproprietary Names (INN) for pharmaceutical substances, 2024, WHO](https://www.who.int/publications/i/item/9789240099388)
6. [International nonproprietary names for monoclonal antibodies: an evolving nomenclature system, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC9122354/)
7. [Strengthening Signal Detection in Pharmacovigilance by Using International Nonproprietary Name (INN) Stems, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC13002644/)
8. [The INN global nomenclature of biological medicines: A continuous challenge, ScienceDirect](https://www.sciencedirect.com/science/article/pii/S104510561930048X)
9. [Guidance on the establishment of new INN stems, WHO](https://www.who.int/publications/i/item/inn-07-215)
10. [INN Programme: Nomenclature schemes for advanced therapies, WHO](https://www.who.int/docs/default-source/international-nonproprietary-names-%28inn%29/nomenclature-schemes-advanced-therapies-201707.pdf)
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*Topic: Encyclopedia › Life and health › Applied biology and nonhuman health › Veterinary medicine and animal health › Veterinary pharmacology and therapeutics › Veterinary drug regulation and pharmacovigilance › Classification and coding of veterinary medicines*
*Initially written Sep 17, 2026 · Reviewed: Oct 21, 2026 · Edited: Oct 15, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*
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