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Created page with "{{Short description|Drug classification system}} The '''Anatomical Therapeutic Chemical (ATC) Classification System''' is a drug classification system that classifies the active ingredients of drugs according to the organ or system on which they act and their therapeutic, pharmacological and chemical properties. Its purpose is an aid to monitor drug use and for Drug devel..."

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{{Short description|Drug classification system}}
The '''Anatomical Therapeutic Chemical (ATC) Classification System''' is a [[drug classification]] system that classifies the [[Medication|active ingredient]]s of [[drug]]s according to the [[organ (anatomy)|organ]] or [[system]] on which they act and their [[therapeutic]], [[pharmacological]] and chemical properties. Its purpose is an aid to [[Adverse_drug_reaction#Monitoring_bodies|monitor drug use]] and for [[Drug development|research]] to improve quality medication use. It does not imply [[Formulary (pharmacy)|drug recommendation]] or [[efficacy]].<ref>{{cite web |title=Purpose of the ATC/DDD system |url=https://www.whocc.no/atc_ddd_methodology/purpose_of_the_atc_ddd_system/ |website=WHO Collaborating Centre for Drug Statistics Methodology |access-date=6 July 2021}}</ref> It is controlled by the [[World Health Organization]] Collaborating Centre for Drug Statistics Methodology (WHOCC), and was first published in 1976.<ref name="history">{{cite web|url=http://www.whocc.no/atc_ddd_methodology/history/|publisher=WHO Collaborating Centre for Drug Statistics Methodology|title=ATC/DDD Methodology: History}}</ref><ref>{{cite web | author=WHOCC | title=ATC alterations from 2005-2019 | website=WHO Collaborating Centre for Drug Statistics Methodology (WHOCC) | date=28 November 2019 | url=https://www.whocc.no/atc_ddd_alterations__cumulative/atc_alterations/ | access-date=27 December 2019}}</ref><ref>{{cite web | author=WHOCC | title=DDD alterations from 2005-2019 | website=WHO Collaborating Centre for Drug Statistics Methodology (WHOCC) | date=28 November 2018 | url=https://www.whocc.no/atc_ddd_alterations__cumulative/ddd_alterations/ | access-date=27 December 2019}}</ref>

== Coding system ==
This [[Pharmaceutical code|pharmaceutical coding system]] divides drugs into different groups according to the organ or system on which they act, their [[medicine|therapeutic]] intent or nature, and the drug's [[chemical classification|chemical characteristics]]. Different brands share the same code if they have the same active substance and indications. Each bottom-level ATC code stands for a pharmaceutically used substance, or a combination of substances, in a single indication (or use). This means that one drug can have more than one code, for example [[acetylsalicylic acid]] (aspirin) has {{ATC|A01|AD05}} as a drug for local [[mouth|oral]] treatment, {{ATC|B01|AC06}} as a [[platelet inhibitor]], and {{ATC|N02|BA01}} as an [[analgesic]] and [[antipyretic]]; as well as one code can represent more than one active ingredient, for example {{ATC|C09|BB04}} is the combination of perindopril with amlodipine, two active ingredients that have their own codes ({{ATC|C09|AA04}} and {{ATC|C08|CA01}} respectively) when prescribed alone.

The ATC classification system is a strict hierarchy,<ref name="ncbi.nlm.nih.gov">{{cite journal |last1=Cimino |first1=James |title=Desiderata for Controlled Medical Vocabularies in the Twenty-First Century |journal=Methods of Information in Medicine |date=Nov 1998 |volume=37 |issue=4–5 |pages=394–403 |doi=10.1055/s-0038-1634558 |pmid=9865037 |pmc=3415631 }}</ref> meaning that each code necessarily has one and only one parent code, except for the 14 codes at the topmost level which have no parents. The codes are semantic identifiers,<ref name="ncbi.nlm.nih.gov"/> meaning they depict information by themselves beyond serving as identifiers (namely, the codes depict themselves the complete lineage of parenthood). As of 7 May 2020, there are 6,331 codes in ATC; the table below gives the count per level.<ref>{{cite web |last1=Kury |first1=Fabrício |title=Scrape Anatomical-Therapeutic-Chemical (ATC) classes from the WHO Collaborating Centre for Drug Statistics Methodology website |url=https://github.com/fabkury/atcd |website=GitHub |access-date=7 May 2020}}</ref>

{| class="wikitable"
|-
! ATC level !! Codes !! Different names/pharmaceuticals
|-
| Level 1 || 14 || 14
|-
| Level 2 || 94 || 94
|-
| Level 3 || 267 || 262
|-
| Level 4 || 889 || 819
|-
| Level 5 || 5067 || 4363
|}

== History ==
The ATC system is based on the earlier Anatomical Classification System, which is intended as a tool for the pharmaceutical industry to classify pharmaceutical products (as opposed to their active ingredients).<ref>{{cite web|url=http://www.ephmra.org/user_uploads/who-atc%202013%20final.pdf|title=Comparison of the WHO ATC Classification & EphMRA/Intellus Anatomical Classification|publisher=EphMRA|access-date=7 January 2017|archive-url=https://web.archive.org/web/20150806235351/http://www.ephmra.org/user_uploads/who-atc%202013%20final.pdf|archive-date=6 August 2015|url-status=dead}}</ref> This system, confusingly also called ATC, was initiated in 1971 by the [[European Pharmaceutical Market Research Association]] (EphMRA) and is being maintained by the EphMRA and Intellus. Its codes are organised into four levels.<ref>{{cite web|url=http://www.ephmra.org/user_uploads/atcguidelines2016final.pdf|title=EphMRA Anatomical Classification Guidelines 2018|access-date=2017-01-07|archive-url=https://web.archive.org/web/20160423224519/http://www.ephmra.org/user_uploads/atcguidelines2016final.pdf|archive-date=2016-04-23|url-status=dead}}</ref> The WHO's system, having five levels, is an extension and modification of the EphMRA's. It was first published in 1976.<ref name="history"/>

== Classification ==
In this system, drugs are classified into groups at five different levels:<ref>{{cite web|url=http://www.whocc.no/atc/structure_and_principles/|publisher=WHO Collaborating Centre for Drug Statistics Methodology|title=ATC: Structure and principles}}</ref>

=== First level ===
The first level of the code indicates the anatomical main group and consists of one letter. There are 14 main groups:<ref>{{cite web|url=http://www.whocc.no/atc_ddd_index/|publisher=WHO Collaborating Centre for Drug Statistics Methodology|title=ATC/DDD Index}}</ref>

{| class="wikitable"
|-
!Code
!Contents
|-
| '''[[ATC code A|A]]'''
| [[Alimentary tract]] and [[metabolism]]
|-
| '''[[ATC code B|B]]'''
| [[Blood]] and [[haematopoiesis|blood forming organs]]
|-
| '''[[ATC code C|C]]'''
| [[Cardiovascular system]]
|-
| '''[[ATC code D|D]]'''
| [[Dermatological]]s
|-
| '''[[ATC code G|G]]'''
| [[Genito-urinary system]] and [[sex hormone]]s
|-
| '''[[ATC code H|H]]'''
| Systemic [[Hormone|hormonal]] preparations, excluding sex hormones and insulins
|-
| '''[[ATC code J|J]]'''
| [[Antiinfective]]s for systemic use
|-
| '''[[ATC code L|L]]'''
| [[Antineoplastic]] and [[immunomodulator|immunomodulating]] agents
|-
| '''[[ATC code M|M]]'''
| [[Musculo-skeletal system]]
|-
| '''[[ATC code N|N]]'''
| [[Nervous system]]
|-
| '''[[ATC code P|P]]'''
| [[Antiparasitic]] products, [[insecticide]]s and [[insect repellent|repellent]]s
|-
| '''[[ATC code R|R]]'''
| [[Respiratory system]]
|-
| '''[[ATC code S|S]]'''
| [[Sensory organ]]s
|-
| '''[[ATC code V|V]]'''
| Various
|}

''Example'': [[ATC code C|'''C''']] [[Cardiovascular system]]

=== Second level ===
The second level of the code indicates the therapeutic subgroup and consists of two digits.<ref>[https://www.sdrugs.com/?c=atc&n=0 the Anatomical Therapeutic Chemical (ATC) classification system Structure]</ref>

''Example'': [[ATC code C03|C'''03''']] [[Diuretic]]s

=== Third level ===
The third level of the code indicates the therapeutic/pharmacological subgroup and consists of one letter.

''Example'': C03'''C''' High-ceiling diuretics

=== Fourth level ===
The fourth level of the code indicates the chemical/therapeutic/pharmacological subgroup and consists of one letter.

''Example'': C03C'''A''' [[Sulfonamide (medicine)|Sulfonamide]]s

=== Fifth level ===
The fifth level of the code indicates the chemical substance and consists of two digits.

''Example'': C03CA'''01''' [[furosemide]]

==Other ATC classification systems==
=== ATCvet ===
The ''Anatomical Therapeutic Chemical Classification System for veterinary medicinal products'' (ATCvet) is used to classify [[veterinary]] drugs. ATCvet codes can be created by placing the letter Q in front of the ATC code of most human medications. For example, furosemide for veterinary use has the code '''Q'''C03CA01.

Some codes are used exclusively for veterinary drugs, such as ''[[ATCvet code QI|QI]] Immunologicals'', ''[[ATCvet code QJ51|QJ51]] Antibacterials for intramammary use'' or ''QN05AX90 [[amperozide]]''.<ref>{{cite web|url=http://www.whocc.no/atcvet/atcvet/|publisher=WHO Collaborating Centre for Drug Statistics Methodology|title=ATCvet|access-date=2015-02-15|archive-url=https://web.archive.org/web/20150413113407/http://www.whocc.no/atcvet/atcvet/|archive-date=2015-04-13|url-status=dead}}</ref>

=== Herbal ATC (HATC) ===
The Herbal ATC system (HATC) is an ATC classification of [[Herbal medicine|herbal substances]]; it differs from the regular ATC system by using 4 digits instead of 2 at the 5th level group.<ref>{{cite web |title=The Herbal Anatomical Therapeutic Chemical Classification System |url=https://www.who-umc.org/whodrug/whodrug-portfolio/whodrug-global/herbal-atc/ |website= [[Uppsala Monitoring Centre]] |access-date=7 July 2021 }}</ref>

The herbal classification is not adopted by WHO. The [[Uppsala Monitoring Centre]] is responsible for the Herbal ATC classification, and it is part of the [[WHO Drug Dictionary|WHODrug Global]] portfolio available by [[Subscription business model|subscription]].<ref>{{cite web |title=WHODrug portfolio |url=https://www.who-umc.org/whodrug/whodrug-portfolio/ |website=[[Uppsala Monitoring Centre]] |access-date=6 July 2021}}</ref>

== Defined daily dose ==
{{main|Defined daily dose}}
The ATC system also includes defined daily doses (DDDs) for many drugs. This is a measurement of drug consumption based on the usual daily dose for a given drug. According to the definition, "[t]he DDD is the assumed average maintenance dose per day for a drug used for its main indication in adults."<ref>{{cite web|url=http://www.whocc.no/ddd/definition_and_general_considera/|publisher=WHO Collaborating Centre for Drug Statistics Methodology|title=DDD: Definition and general considerations}}</ref>

==Adaptations and updates==
National issues of the ATC classification, such as the [[Germany|German]] ''Anatomisch-therapeutisch-chemische Klassifikation mit Tagesdosen'', may include additional codes and DDDs not present in the WHO version.<ref>{{cite web|url=http://www.dimdi.de/static/de/klassi/atcddd/atc-gesetze.htm|publisher=Deutsches Institut für Medizinische Dokumentation und Information|title=ATC-Klassifikation mit DDD: Gesetzlicher Hintergrund|language=de|access-date=2010-02-14|archive-url=https://web.archive.org/web/20160303174835/http://www.dimdi.de/static/de/klassi/atcddd/atc-gesetze.htm|archive-date=2016-03-03|url-status=dead}}</ref>

ATC follows guidelines<ref>{{cite web|title=Guidelines for ATC classification and DDD assignment|date=2020-12-16|publisher=WHO Collaborating Centre for Drug Statistics Methodology|url=https://www.whocc.no/atc_ddd_index_and_guidelines/guidelines/| access-date = 2021-06-15}}</ref> in creating new codes for newly approved drugs. An application is submitted to WHO for ATC classification and DDD assignment. A preliminary or temporary code is assigned and published on the website and in the ''WHO Drug Information'' for comment or objection. New ATC/DDD codes are discussed at the semi-annual Working Group meeting. If accepted it becomes a final decision and published semi-annually on the website and ''WHO Drug Information'' and implemented in the annual print/on-line ACT/DDD Index on January 1.<ref>{{cite web|title=New ATC 5th levels|date=2021-05-04|publisher=WHO Collaborating Centre for Drug Statistics Methodology|url=https://www.whocc.no/lists_of__temporary_atc_ddds_and_alterations/new_atc_5th_levels/|access-date=2021-06-18}}</ref>

Changes to existing ATC/DDD follow a similar process to become temporary codes and if accepted become a final decision as ATC/DDD alterations. ATC and DDD alterations are only valid and implemented in the coming annual updates; the original codes must continue until the end of the year.

An updated version of the complete on-line/print ATC index with DDDs is published annually on January 1.<ref>{{cite web| url=https://www.whocc.no/atc_ddd_index_and_guidelines/atc_ddd_index/| title= ATC Index with DDDs | date=2020-12-16 |publisher=WHO Collaborating Centre for Drug Statistics Methodology| access-date = 2020-06-15}}</ref>

== See also ==
* [[Classification of Pharmaco-Therapeutic Referrals]] (CPR)
* [[ICD-10]] International Classification of Diseases
* [[International Classification of Primary Care]] (ICPC-2) / [[ICPC-2 PLUS]]
* [[Medical classification]]
* [[Pharmaceutical care]]
* [[Pharmacotherapy]]
* [[RxNorm]]

== References ==
{{reflist}}

== External links ==
* {{Official website|url=http://www.whocc.no}}
* {{cite web |title=''Who Drug Information'' | url=https://www.who.int/our-work/access-to-medicines-and-health-products/who-drug-information | publisher = [[World Health Organization]] | access-date = 22 June 2021 }} Quarterly journal providing an overview of topics relating to medicines development and regulation.
* {{cite web|url=https://www.sydney.edu.au/dam/corporate/documents/faculty-of-medicine-and-health/research/centres-institutes-groups/caps-brochure.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.sydney.edu.au/dam/corporate/documents/faculty-of-medicine-and-health/research/centres-institutes-groups/caps-brochure.pdf |archive-date=2022-10-09 |url-status=live|title=ATC: Introduction - page 2 of CAPS|publisher=Family Medicine Research Centre}} from {{cite web|title=Health classifications and terminologies - CAPS - Coding Atlas for Pharmaceutical Substances|url=https://www.sydney.edu.au/medicine-health/our-research/research-centres/who-collaborating-centre-for-strengthening-rehabilitation-capacity-in-health-systems/classifications-and-terminologies.html|publisher=Faculty of Medicine and Health [[University of Sydney]]|access-date=18 June 2021}}
* [http://www.ephmra.org/Classification EphMRA Anatomical Classification (ATC and NFC)]
* [https://github.com/fabkury/atcd atcd]. [[R_(programming language)|R]] script to scrape the ATC data from the WHOCC website; contains link to download entire ATC tree.

{{Major Drug Groups}}
{{Medical classification}}
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{{二次利用|date=9 October 2022}}
[[Category:ATC codes| ]]
[[Category:Drugs by target organ system| ]]
[[Category:Drugs]]
[[Category:Pharmacological classification systems]]
[[Category:World Health Organization]]

Anatomical Therapeutic Chemical Classification System - Revision history