mode of action

{{Short description|Functional/anatomical change at cellular level due to a substance}}

In pharmacology and biochemistry, mode of action (MoA) describes a functional or anatomical change, resulting from the exposure of a living organism to a substance. In comparison, a mechanism of action (MOA) describes such changes at the molecular level.{{cite web|title=Mechanisms and mode of dioxin action | url= http://www.epa.gov/ncea/pdfs/dioxin/nas-review/pdfs/part3/dioxin_pt3_ch03_oct2004.pdf | publisher = US EPA | access-date=11 June 2012 | archive-url = https://web.archive.org/web/20150226023800/http://www.epa.gov/ncea/pdfs/dioxin/nas-review/pdfs/part3/dioxin_pt3_ch03_oct2004.pdf | archive-date= 26 February 2015 | url-status = dead }}{{cite book | editor-last1 = McQueen | editor-first1 = Charlene A. | title = Comprehensive Toxicology | date = 2010 | publisher = Elsevier | location = Oxford | isbn = 978-0-08-046884-6 | edition = 2nd | vauthors = Grant RL, Combs AB, Acosta D | chapter = Experimental Models for the Investigation of Toxicological Mechanisms | chapter-url = https://books.google.com/books?id=jzCAKsa2CpMC&q=mechanism+mode+action+drug+definition+molecular+cellular&pg=PA204 | page = 204 }}

A mode of action is important in classifying chemicals, as it represents an intermediate level of complexity in between molecular mechanisms and physiological outcomes, especially when the exact molecular target has not yet been elucidated or is subject to debate. A mechanism of action of a chemical could be "binding to DNA" while its broader mode of action would be "transcriptional regulation".{{cite journal|last=Ng|first=Wai-Leung|author2=Krystyna M. Kazmierczak |author3=Gregory T. Robertson |author4=Raymond Gilmour |author5=Malcolm E. Winkler |title=Transcriptional Regulation and Signature Patterns Revealed by Microarray Analyses of Streptococcus Pneumoniae R6 Challenged with Sublethal Concentrations of Translation Inhibitors| journal = Journal of Bacteriology | volume = 185 | issue = 1 | pages = 359–70 | date = Jan 2003 | pmid = 12486074 | doi = 10.1128/JB.185.1.359-370.2003 | pmc=141824}} However, there is no clear consensus and the term mode of action is also often used, especially in the study of pesticides, to describe molecular mechanisms such as action on specific nuclear receptors or enzymes.{{cite web | title = Herbicide Group Classification by Mode of Action | url = http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm6487 | publisher = Alberta Agriculture and Rural Development | access-date = 11 June 2012 | archive-url=https://web.archive.org/web/20190123004800/http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/prm6487 | archive-date=2019-01-23}}{{cite web | url=http://www.frac.info/docs/default-source/publications/frac-code-list/frac-code-list-2021--final.pdf | title=FRAC Code List ©*2021: Fungal control agents sorted by cross resistance pattern and mode of action (including coding for FRAC Groups on product labels) | date=March 2021 | author=FRAC (Fungicide Resistance Action Committee) | access-date=2021-04-02 | archive-date=2021-11-05 | archive-url=https://web.archive.org/web/20211105005300/https://www.frac.info/docs/default-source/publications/frac-code-list/frac-code-list-2021--final.pdf | url-status=dead }}{{cite web | url=http://wssa.net/wp-content/uploads/WSSA-Mechanism-of-Action.pdf | title=Summary of Herbicide Mechanism of Action According to the Weed Science Society of America (WSSA) | author=Weed Science Society of America | access-date=2021-04-02 | archive-date=2022-10-08 | archive-url=https://web.archive.org/web/20221008132104/https://www.wssa.net/wp-content/uploads/WSSA-Mechanism-of-Action.pdf | url-status=live }}{{cite web | url=http://www.weedscience.org/Documents/ShowDocuments.aspx?DocumentID=1192 | title=HERBICIDE MODE OF ACTION TABLE | last=Heap | first=Ian | access-date=2021-04-02 | archive-date=2022-07-05 | archive-url=https://web.archive.org/web/20220705133439/https://weedscience.org/Documents/ShowDocuments.aspx?DocumentID=1192 | url-status=live }}{{cite web | title=HRAC MOA 2020 Revision Description and Master Herbicide List | website=Herbicide Resistance Action Committee | date=2020-09-14 | url=http://hracglobal.com/tools/hrac-moa-2020-revision-description-and-master-herbicide-list | access-date=2021-04-01 | archive-date=2023-01-15 | archive-url=https://web.archive.org/web/20230115130638/https://hracglobal.com/tools/hrac-moa-2020-revision-description-and-master-herbicide-list | url-status=live }}{{cite web | title=Interactive MoA Classification | website=Insecticide Resistance Action Committee | date=2020-09-16 | url=http://irac-online.org/modes-of-action/ | access-date=2021-04-01 | archive-date=2022-08-08 | archive-url=https://web.archive.org/web/20220808102513/https://irac-online.org/modes-of-action/ | url-status=live }}{{cite web | url=http://www.epa.gov/sites/production/files/2017-09/documents/prn-2017-1-pesticide-resistance-management-labeling.pdf | title=PESTICIDE REGISTRATION NOTICE (PRN) 2017-1 NOTICE TO MANUFACTURERS, PRODUCERS, PRODUCERS AND REGISTRANTS OF PESTICIDE PRODUCTS AND DEVICES | author=United States Environmental Protection Agency | access-date=2021-04-02 | archive-date=2021-03-23 | archive-url=https://web.archive.org/web/20210323143812/https://www.epa.gov/sites/production/files/2017-09/documents/prn-2017-1-pesticide-resistance-management-labeling.pdf | url-status=live }} Despite this, there are classification attempts, such as the HRAC's classification to manage pesticide resistance.{{cite web |title=PROTECTING CROP YIELDS AND QUALITY WORLDWIDE |url=https://hracglobal.com/ |website=Herbicide Resistance Action Committee |language=en}}