When I use a word . . . Naming medicines—mixtures and co-names

Abstract

A medicine can have up to four types of names: Name 1—what the medicine is, as indicated by its full chemical name; Name 2—what the medicine’s name is, i.e. its generic name, such as that assigned by the World Health Organization, its International Nonproprietary Name (INN); Name 3—what the medicine’s name is called, i.e. any brand names assigned by a pharmaceutical company; Name 4—what the medicine itself is called, i.e. colloquial names given to it by the general public, such as street names for recreational drugs and drugs of abuse. The INN is the most important of these. It establishes for each individual medicine a single name that can be used and recognised globally. Each INN is constructed with, among other things, patient safety in mind. Mixtures of medicines in a single formulation are not given INNs. However, since 1971 in the UK 26 single names have been given to mixtures of drugs, usually two compounds, by combining the prefix co- with syllables taken from the drugs in the mixture. For example, co-amoxiclav contains a mixture of amoxicillin and clavulanic acid. This has sometimes led to serious prescribing errors, when, for example, co-amoxiclav was given to people with penicillin allergy. When using a formulation that is labelled with a co-name, prescribers should ensure that they know what the contents of the mixture are. Conversely, when the label on a package specifies the ingredients of a mixture by listing each name, but does not specify the co-name, it is important that prescribers know what the corresponding co-name was.