At present, medicines on the Model List are listed alphabetically under 27 main therapeutic use categories. Although this system of sectioning may not have the rigour of alternative systems, for example, the Anatomical Therapeutic Chemical (ATC) classification in which medicines are divided into different groups according to the organ or system on which they act (17), it is widely used by supply agencies and for national lists of essential medicines. Any decision to change the current system of section headings and/or numberings in the Model List should therefore be taken with great care.

At its present meeting, the Committee considered promoting and adopting the ATC classification for the Model List, but concluded that, although the ATC system was not only widely supported and promoted by WHO but was also gaining acceptance as a global classification system, its adoption would only be acceptable if essential information about the classification was freely available in the public domain. Currently, this is not the case. The Committee also noted that information relating to the 5-level ATC code number for each item in the Model List is probably less relevant than the logic of the classification system itself. The Committee thus recommended not to add the ATC code numbers to the Model List itself, but to list separately the items on the Model List with their corresponding 5-level ATC code numbers (see Annex 3). This approach would allow a gradual introduction of the ATC system and leave international organizations, such as UNICEF, with the option to maintain the old system or to change to the ATC classification. The Committee also recommended that WHO should actively pursue ways and means of putting the relevant information on the ATC system in the public domain.