the Anatomical Therapeutic Chemical (ATC) classification system
Version for 2006
(World Health Organization)

Structure

In the Anatomical Therapeutic Chemical (ATC) classification system, the drugs are divided into different groups according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties.
Drugs are classified in groups at five different levels. The drugs are divided into fourteen main groups (1st level), with one pharmacological/therapeutic subgroup (2nd level). The 3rd and 4th levels are chemical/pharmacological/therapeutic subgroups and the 5th level is the chemical substance. The 2nd, 3rd and 4th levels are often used to identify pharmacological subgroups when that is considered more appropriate than therapeutic or chemical subgroups.
The complete classification of metformin illustrates the structure of the code:
A Alimentary tract and metabolism
(1st level, anatomical main group)
A10 Drugs used in diabetes
(2nd level, therapeutic subgroup. Consists of two digits)
A10B Oral blood glucose lowering drugs
(3rd level, pharmacological subgroup)
A10BA Biguanides
(4th level, chemical subgroup)
A10BA02 Metformin
(5th level, chemical substance)
Thus, in the ATC system all plain metformin preparations are given the code A10BA02.

• A - Alimentary tract and metabolism
• B - Blood and blood forming organs
• C - Cardiovascular system
• D - Dermatologicals
• G - Genito-urinary system and sex hormones
• H - Systemic hormonal preparations, excluding sex hormones and insulins
• J - Anti-infectives for systemic use
• L - Antineoplastic and immunomodulating agents
• M - Musculo-skeletal system
• N - Nervous system
• P - Antiparasitic products, insecticides and repellents
• Q - Veterinary drug
• R - Respiratory system
• S - Sensory organs
• V - Various