Anatomical Therapeutic Chemical Classification System

The Anatomical Therapeutic Chemical (ATC) Classification System is an integral drug classification system that assigns the active ingredients of drugs based on the organ or system they target, as well as their therapeutic, pharmacological, and chemical properties. This system is regulated and maintained by the World Health Organization Collaborating Centre for Drug Statistics Methodology (WHOCC). It was introduced to the world for the first time in 1976.

Overview

The primary intent of the ATC system is to provide a standardized approach to classify drugs. This pharmaceutical coding system categorizes medications into different groups based on:

The organ or system they act upon Their therapeutic purpose or characteristics Their chemical properties What's intriguing about this system is that multiple brands having the same active substance and indications will share the same code. Moreover, a single ATC code can represent a specific pharmaceutically active substance or even a combination of substances in a single indication. For instance, acetylsalicylic acid (aspirin) has multiple codes: A01AD05 (WHO)

for local oral treatments, B01AC06 (WHO)
as a platelet inhibitor, and N02BA01 (WHO)
as an analgesic and antipyretic. Similarly, one ATC code can correspond to several active ingredients. The code C09BB04 (WHO)

, for example, represents the combination of perindopril and amlodipine. However, when prescribed individually, they have their unique codes as C09AA04 (WHO)

and C08CA01 (WHO)

, respectively.

The structure of the ATC system is strictly hierarchical. Each code has a single parent code, with the exception of the 14 top-tier codes, which do not have any parent code. Importantly, the codes function as semantic identifiers. This means they provide complete lineage information about their hierarchical position.

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History

The inception of the ATC system has its roots in the earlier Anatomical Classification System. This system, developed as a tool for the pharmaceutical industry, focused on classifying pharmaceutical products based on their properties rather than their active ingredients. This previous system, also termed ATC, was initiated in 1971 by the European Pharmaceutical Market Research Association (EphMRA). Maintained by EphMRA and Intellus, its classification involved four levels of hierarchy. The modern ATC system, established by WHO, enhanced and modified this structure, adding a fifth level of classification. It was formally published in 1976.

Classification

The ATC system breaks down drugs into five distinct levels of classification:

First level

Representing the anatomical main group, the first level comprises one letter. There are 14 primary groups in total:

Code	Contents
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	Sense organs
V	Various

Second level

This level, represented by two numbers, showcases the therapeutic main group. For instance, ATC code N05 stands for psycholeptics.

Third level

At the third level, represented by one letter, the therapeutic/pharmacological subgroup is highlighted. Taking ATC code N05B as an example, it encompasses anxiolytics.

Fourth level

The chemical/therapeutic/pharmacological subgroup is denoted at this level, which is also represented by a single letter. ATC code N05BA pertains to benzodiazepine derivatives.

Fifth level

This final level, represented by two numbers, specifies the chemical substance. For instance, ATC code N05BA01 designates diazepam.

Usage

Given the comprehensiveness and universal applicability of the ATC system, it is extensively employed for drug utilization research. This ensures that prescriptions and drug consumption statistics can be compared and analyzed across countries, facilitating a more precise understanding of drug use patterns.

Moreover, its hierarchical structure allows for data aggregation at different levels. This means researchers can focus on broader drug categories, like all cardiovascular drugs, or drill down to specific active ingredients.

External links

• World Health Organization Collaborating Centre for Drug Statistics Methodology

Anatomical Therapeutic Chemical Classification System Resources
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