What is ATC system and how we classify drugs in our report?

What is ATC system and how we classify drugs in our report?

Written by: Nermin Đuzić, M.Sc. in Genetics, Content Specialist

Peer-reviewed by: Edin Hamzić, Ph.D. in Genetics, Chief Science Officer

In our previous articles we explained how our pharmacogenomics report looks like and how can you navigate through it. You noticed that it contains drug class and drug category amongst the other information regarding the corresponding drug. All drugs in our report come from Pharmacogenomics Knowledge Base, and are divided to classes and categories.

What is drug category & class?

Drug category refers to a type of drug from a medical perspective, according to organic systems and conditions they are used to treat. Drug class represents the categorization from a pharmacological perspective, mechanism of action and the biological target. 

We rely on the Anatomical Therapeutical Chemical (ATC) classification system, according to which drugs and their active substances are divided into different groups based on organs or systems they affect and their therapeutic, chemical and pharmacological properties. What we consider as a drug category is actually an anatomical group in the above-mentioned ATC classification system, and drug class is a pharmacological subgroup.

What is ATC classification system?

The Anatomical Therapeutic Classification (ATC) system is a widely-used method for organizing and categorizing drugs according to their therapeutic and pharmacological properties. Developed by the World Health Organization (WHO), the ATC system is designed to provide a standardized system for organizing drugs and other medical products, which can be used for a variety of purposes, including prescribing, dispensing, and research.

How does it work?

The ATC system is hierarchical, with each drug being assigned to a specific category at five different levels. Each level has more specific and informative subgroups. The five levels are: 

  1. Anatomical main group - grouping of drugs according to their anatomical systems or organs which they act upon. For example, drugs that act on the cardiovascular system would be assigned to the cardiovascular main group. There are fourteen main anatomical groups, as shown in Table 1 below.
Table 1: List of Anatomical groups according to ATC system


Anatomical group / category


Alimentary tract and metabolism


Blood and blood forming organs


Cardiovascular system




Genito-urinary system and sex hormones


Systemic hormonal preparations, excluding sex hromones and insulinsm


Antiinfective for systemic use


Antineoplastic and immunomodulating agents


Musculo-skeletal system


Nervous system


Antiparasitic products, insecticides and repellents


Respiratory system


Sensory organs



  1. Therapeutic main group - grouping of drugs according to their pharmacological, chemical, or therapeutic activity. For example, drugs that are used to treat high blood pressure would be assigned to the antihypertensive subgroup.
  1. Pharmacological subgroup - grouping of drugs according to their particular type of pharmacological action and properties. For example, drugs that work by inhibiting the enzyme ACE would be assigned to the angiotensin converting enzyme (ACE) inhibitor subgroup.
  1. Chemical substance - grouping of drugs according to their chemical structure and composition, which can be useful for research and development purposes.
  1. Chemical substance with pharmacological activity - grouping of drugs according to their specific active ingredient.

ATC codes

In addition to the hierarchical structure, the ATC system also uses codes to identify each drug. These codes consist of a letter and several numbers, and provide a unique identifier for each drug. For example, the code "C09AA05" would represent an ACE inhibitor in the chemical substance subgroup.

Let’s give another example on drug metformin, this time in more detail. All plain metformin preparations are given the code A10BA02 in ATC. This code means the following:

Table 2: Example of ATC code breakdown (taken from Anatomical Therapeutic Chemical (ATC) Classification (who.int))

Code / Letter

Classification category name



Alimentary tract and metabolism

1st level, anatomical main group


Drugs used in diabetes

2nd level, therapeutic subgroup


Blood glucose lowering drugs, excl. insulins

3rd level, pharmacological subgroup



4th level, chemical subgroup



5th level, chemical substance

Overall, the ATC system is a valuable tool for organizing and classifying drugs, and is used by healthcare providers, researchers, and regulatory agencies around the world. It allows for the efficient and consistent classification of drugs.


The ATC classification system is widely used in pharmacology and toxicology research, as it provides a standardized way to classify and compare the properties of different drugs. It is also used in drug information systems, such as databases and prescribing software, to facilitate the identification and selection of appropriate medications for patients. 

Additionally, the ATC classification system is used in the development of treatment guidelines and drug formularies, which are lists of drugs that are recommended or approved for use in a particular setting or for a specific condition.

In addition to its uses in research and clinical practice, the ATC classification system is also used in the regulatory process for drugs and medical products. Regulatory agencies, such as the Food and Drug Administration (FDA) in the United States, use the ATC classification system to evaluate the safety and effectiveness of drugs and to ensure that they are labeled and marketed correctly.

Overall, the ATC classification system is an important tool for organizing and comparing the therapeutic, pharmacological, and chemical properties of drugs and other medical products. It helps health care professionals, researchers, and regulatory agencies to identify, classify, and evaluate the effectiveness and safety of these products, and ultimately to improve the quality of care for patients.

*Disclaimer: The term “drug” in the above article refers to a chemical substance used to treat, cure, diagnose or prevent a disease or condition. Alternatives for this term include medication, pharmaceutical or therapeutic agents. In this context, “drug” does not refer to any type of illegal stimulant or recreational drug.

Back to blog

Check out some of our DNA kits below.

1 of 3