Anatomical, therapeutic, chemical classification

A classification system of medicines where the active ingredients are divided into different groups according to the organ or system on which they act and their chemical, pharmacological and therapeutic properties. Medicines are classified on 5 specified levels (ATC 1, ATC 2, ATC 3, ATC 4 and ATC 5) of which the first level divides medicines into fourteen main groups . ATC 2 specifies the therapeutic subgroups (e.g. drugs used in diabetes). ATC 3 and 4 indicate the pharmacological and chemical subgroup, respectively (e.g. oral blood glucose lowering drugs and biguanides, respectively) and ATC 5 is the chemical active substance (e.g. metformine). The 2nd, 3rd and 4th levels are often used to identify pharmacological subgroups when that is considered more appropriate than therapeutic or chemical subgroups. Cf. reference group, reference price system