The Anatomical Therapeutic Chemical (ATC) classification system is a drug classification system that divides active ingredients in drugs based on the specific organs or systems on which they work and on their therapeutic, pharmacological, and chemical qualities. The ATC classification system aims to assist in conducting drug monitoring and research that can ultimately improve the quality of medicines.

The ATC system is based on the earlier Anatomical Classification method, which had been designed to help the pharmaceutical industry classify various medicinal products (rather than active ingredients).

The ATC classification system involves five (05) levels, with the first level being the main anatomical/pharmacological category and the final, fifth level being the chemical substance. The classification of the levels is as follows:

  • First Level: This level consists of fourteen (14) major anatomical or pharmacological groupings.
  • Second Level: Each first-level group is further subdivided into second-level groups, which can be either pharmacological or therapeutic in nature.
  • Third and Fourth Levels: These levels encompass chemical, pharmacological, or therapeutic groups.
  • Fifth Level: This level consists of the chemical compound.

Pharmaceutical substances are categorized based on their primary therapeutic applications, with just one (01) ATC code assigned to each medical product, as defined by the method of administration and, in some cases, strength. Medicinal substances sometimes contain multiple ATC codes that signify distinct methods of administration and therapeutic applications. As pharmacological categories have been placed at the second, third, and fourth levels of the ATC system, medicines with several therapeutic applications can be included without defining their primary indication.

How is the ATC System Related to the WHO?

The World Health Organization (WHO) Collaborating Centre for Drug Statistics Methodology is the administrative body responsible for developing and maintaining the Anatomical Therapeutic Chemical (ATC) classification system. The WHO Collaborating Centre in Oslo creates new entries in the ATC classification system based on requests from individual researchers, pharmaceutical firms, and Regulatory agencies. The primary objective of the WHO in maintaining the ATC system is to provide aid for drug monitoring and research and improve the overall quality of drugs in the pharmaceutical industry.

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