ATC classification system

The Anatomical Therapeutic Chemical (ATC) classification system classifies drugs according to the organ or system on which they act.
Drugs are classified into groups at five levels.
First level: a letter indicates the anatomical group
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 => Antiinfectives for systemic use
L => Antineoplastic and immunomodulating agents
M => Musculo skeletal system
N => Nervous system
P => Antiparasitic products, insecticides and repellents
R => Respiratory system
S => sensory organs
V => various
Second level: 2 digits indicate the therapeutic subgroup
Third level: 1 letter indicates the therapeutic pharmacological subgroup
Fourth level: 1 letter indicates the chemical therapeutic pharmacological subgroup
Fifth level: 2 digits indicate the chemical substance
Example: J01CA04 Amoxicillin
J = Antiinfective for systemic use
01 = therapeutic subgroup
C = therapeutic pharmacological subgroup
A = chemical therapeutic pharmacological subgroup
04 = chemical substance