Classification system anatomical therapeutic chemical (Anatomical Therapeutic Chemical Classification System) refer to the ATC, a system of classification of medicinal is that in which the medications based on the organ or system on which its effect, and also taking into account the peculiarities of medical, pharmacological, chemical, etc. in five different levels, divided into.
in the first level of this division., the fourteen main groups anatomical have taken place and each with a letter, are specified.
in Level II, subgroup therapy is also marked with the combination of two numbers expressed in.
at the level of the third subgroup pharmacological also marked with a letter expression.
in the fourth level, etc. subclass chemical also with a letter other, specify.....
in the fifth level, and. chemical for the dedicated and with a combination of two numbers expressed in.

for example, on the basis of this system Classification, Code N02AC52 expresses the drug methadone in the application of the housing.