International Nonproprietary Name

An International Nonproprietary Name (INN; also known as rINN, for recommended International Nonproprietary Name, a name which is still under consideration being known as a pINN for proposed International Nonproprietary Name) is an official nonproprietary or generic name given to a pharmaceutical substance, as designated by the World Health Organization (WHO). The plethora of named proprietary preparations containing a given substance can lead to confusion about the identity of the active ingredient. INNs facilitate communication by providing a standard name for each substance; they are designed to be unique and distinct so as to avoid confusion in prescribing. A similar role is played in chemistry by IUPAC names, though those are less suited to common usage, being typically very long and unwieldy.

WHO issues INNs in English, Latin, French, Russian, Spanish, Arabic, and Chinese. A drug's INN names are often cognate across most or all of the languages, but they also allow small inflectional, diacritic, and transliterational differences that are usually transparent and trivial for nonspeakers (as is true of most international scientific vocabulary). For example, although "paracetamolum" (la) has an inflectional difference from "paracetamol" (en), and although "paracétamol" (fr) has a diacritic difference, the differences are trivial; users can easily recognize the "same word". And although "парацетамол" (ru) and "paracetamol" (en) have a transliterational difference, they sound similar, and for Russian speakers who can recognize Latin script or English speakers who can recognize Cyrillic script, they look similar; users can recognize the "same word".

Name stems
Drugs from the same therapeutic or chemical class are usually given names with the same stem. Stems are mostly placed word-finally, but in some cases word-initial stems are used. They are collected in a publication informally known as the Stem Book.

Examples are:
 * -anib for angiogenesis inhibitors (e.g. pazopanib)
 * -anserin for serotonin receptor antagonists, especially 5-HT2 antagonists (e.g. ritanserin and mianserin)
 * -arit for antiarthritic agents (e.g. lobenzarit)
 * -ase for enzymes (e.g. asparaginase)
 * -azepam for benzodiazepines (e.g. diazepam and oxazepam)
 * -caine for local anaesthetics (e.g. procaine or cocaine)
 * -cain- for class I antiarrhythmics (e.g. procainamide)
 * -coxib for COX-2 inhibitors, a type of anti-inflammatory drugs (e.g. celecoxib)
 * -mab for monoclonal antibodies (e.g. infliximab); see Nomenclature of monoclonal antibodies
 * -navir for antiretroviral protease inhibitors (e.g. darunavir)
 * -olol for beta blockers (e.g. atenolol)
 * -pril for ACE inhibitors (e.g. captopril)
 * -sartan for angiotensin II receptor antagonists (e.g. losartan)
 * -tinib for tyrosine kinase inhibitors (e.g. imatinib)
 * -vastatin for HMG-CoA reductase inhibitors, a group of cholesterol lowering agents (e.g. simvastatin)
 * -vir for antivirals (e.g. aciclovir or ritonavir)
 * arte- for artemisinin antimalarials (e.g. artemether)
 * cef- for cefalosporins (e.g. cefalexin)
 * io- for iodine containing radiopharmaceuticals (e.g. iobenguane)

Linguistic discussion
The term stem is not used consistently in linguistics. It has been defined as a form to which affixes (of any type) can be attached. Under a different and apparently more common view, this is the definition of a root, while a stem consists of the root plus optional derivational affixes, meaning that it is the part of a word to which inflectional affixes are added. INN stems employ the first definition, while under the more common alternative they would be described as roots.

Name changes
A number of modifications are made to British Approved Names and other older nonproprietary names. This is to ensure similar pronunciation across major languages:


 * ae or oe is replaced by e (e.g. estradiol vs. oestradiol)
 * ph is replaced by f (e.g. amfetamine vs. amphetamine)
 * th is replaced by t (e.g. metamfetamine vs. methamphetamine)
 * y is replaced by i (e.g. aciclovir vs. acyclovir)
 * h and k are avoided where possible