The International Nonproprietary Name (INN) is an official generic and non-proprietary name given to a pharmaceutical drug or an active ingredient. International Nonproprietary Names make communication more precise by providing a unique standard name for each active ingredient, to avoid prescribing errors. The INN system has been coordinated by the World Health Organization (WHO) since 1953.
Having unambiguous standard names for each drug (standardization of drug nomenclature) is important because a drug may be sold by many different brand names, or a branded medication may contain more than one drug. For example, the branded medications Celexa, Celapram and Citrol all contain the same active ingredient: citalopram; and the branded preparation Lemsip contains two active ingredients: paracetamol and phenylephrine.
Each drug's INN is unique but may contain a word stem that is shared with other drugs of the same class, for example the beta blocker drugs propranolol and atenolol share the -olol suffix, and the benzodiazepine drugs lorazepam and diazepam share the -azepam suffix.
The WHO issues INNs in English, Latin, French, Russian, Spanish, Arabic, and Chinese, and a drug's INNs are often cognate across most or all of the languages, with minor spelling or pronunciation differences, for example: paracetamol (en) paracetamolum (la), paracétamol (fr) and парацетамол (ru). An established INN is known as a recommended INN (rINN), while a name that is still being considered is called a proposed INN (pINN).
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.