View source for Acetylcysteine

{{Short description|Medication used to treat overdose of paracetamol}}
{{dist|text=[[N-Acetylcarnosine]], for the proposed treatment of [[cataracts]]}}
{{Use American English|date=October 2024}}
{{Use dmy dates|date=August 2025}}
{{cs1 config|name-list-style=vanc|display-authors=6|mode=cs1}}
{{Infobox drug
| image = Acetylcysteine2.svg
| image_class = skin-invert-image
| width = 125
| alt = 
| image2 = Acetylcysteine-from-xtal-3D-bs-17.png
| image_class2 = bg-transparent
| width2 = 
| alt2 = 
| caption = 

<!-- Clinical data -->
| pronounce = {{IPAc-en|ə|ˌ|s|iː|t|əl|ˈ|s|ɪ|s|t|iː|n}} and similar ({{IPAc-en|ə|ˌ|s|ɛ|t|əl|-|,_|ˌ|æ|s|ᵻ|t|əl|-|,_|-|t|iː|n}})
| tradename = ACC 200, Acetadote, Fluimucil, Mucomyst, others
| Drugs.com = {{drugs.com|monograph|acetylcysteine}}
| MedlinePlus = a615021
| DailyMedID = Acetylcysteine
| pregnancy_AU = B2
| pregnancy_AU_comment = 
| pregnancy_category = 
| routes_of_administration = [[oral administration|Oral]], [[intravenous]], [[Inhalation administration|inhalation]]
| class = 
| ATC_prefix = R05
| ATC_suffix = CB01
| ATC_supplemental = {{ATC|S01|XA08}} {{ATC|V03|AB23}}

<!-- Legal status -->
| legal_AU = S4
| legal_AU_comment = <ref name="DBL Acetylcysteine injection concentrate acetylcysteine 2 g">[http://www.ebs.tga.gov.au/servlet/xmlmillr6?dbid=ebs/PublicHTML/pdfStore.nsf&docid=121503&agid=%28PrintDetailsPublic%29&actionid=1 DBL Acetylcysteine injection concentrate acetylcysteine 2 g/ 10 mL injection ampoule]</ref><ref name="TGA-eB-2022">{{cite web | url=http://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent=&id=CP-2018-PI-01811-1 | title=TGA eBS - Product and Consumer Medicine Information Licence | access-date=30 December 2022 | archive-date=30 December 2022 | archive-url=https://web.archive.org/web/20221230074124/https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent=&id=CP-2018-PI-01811-1 | url-status=live }}</ref><ref name="Healthdirect Australia-2022">{{cite web | title=Acetylcysteine (Omegapharm) | date=30 November 2022 | url=https://www.healthdirect.gov.au/medicines/brand/amt,26341000036106/acetylcysteine-omegapharm | access-date=29 December 2022 | work=Healthdirect Australia | archive-date=30 December 2022 | archive-url=https://web.archive.org/web/20221230074108/https://www.healthdirect.gov.au/medicines/brand/amt,26341000036106/acetylcysteine-omegapharm | url-status=live }}</ref> and Schedule 2<ref>{{cite web | title=Therapeutic Goods (Poisons Standard— June 2025) Instrument 2025 | website=Therapeutic Goods Administration (TGA) | date=May 2025 | url=https://www.legislation.gov.au/F2025L00599/asmade/2025-05-28/text/original/pdf | format=pdf | access-date=31 August 2025}}</ref>
| legal_BR = <!-- OTC, A1, A2, A3, B1, B2, C1, C2, C3, C5, D1, D2, E, F1, F2, F3, F4 -->
| legal_BR_comment = 
| legal_CA = <!-- OTC, Rx-only, Schedule I, II, III, IV, V, VI, VII, VIII -->
| legal_CA_comment = 
| legal_DE = <!-- Anlage I, II, III or Unscheduled -->
| legal_DE_comment = 
| legal_NZ = <!-- Class A, B, C -->
| legal_NZ_comment = 
| legal_UK = POM
| legal_UK_comment = <ref name="(emc)-2022">{{cite web | title=Acepiro 600 mg effervescent tablets - Summary of Product Characteristics (SmPC) | website=(emc) | date=30 August 2022 | url=https://www.medicines.org.uk/emc/product/13849/smpc | access-date=29 December 2022 | archive-date=30 December 2022 | archive-url=https://web.archive.org/web/20221230073232/https://www.medicines.org.uk/emc/product/13849/smpc | url-status=live }}</ref>
| legal_US = Rx-only
| legal_US_comment = <ref name="Acetadote FDA label" />
| legal_EU = 
| legal_EU_comment = 
| legal_UN = <!-- N I, II, III, IV / P I, II, III, IV -->
| legal_UN_comment = 
| legal_status = <!-- For countries not listed above -->

<!-- Pharmacokinetic data -->
| bioavailability = 6–10% (Oral)<ref name="pmid35829920">{{cite journal | vauthors = Tsikas D, Mikuteit M | title = ''N''-acetyl-L-cysteine in human rheumatoid arthritis and its effects on nitric oxide (NO) and malondialdehyde (MDA): analytical and clinical considerations | journal = Amino Acids | volume = 54 | issue = 9 | pages = 1251–1260 | date = September 2022 | pmid = 35829920 | pmc = 9372125 | doi = 10.1007/s00726-022-03185-x }}</ref><ref name="Stockley-2008">{{cite book | vauthors = Stockley RA | title = Chronic Obstructive Pulmonary Disease a Practical Guide to Management. | date = 2008 | publisher = John Wiley & Sons | location = Chichester | isbn = 978-0-470-75528-0 | page = 750 | url = https://books.google.com/books?id=y9li1geShyYC&pg=PA750 | url-status = live | archive-url = https://web.archive.org/web/20170908143219/https://books.google.com/books?id=y9li1geShyYC&pg=PA750 | archive-date = 8 September 2017 }}</ref><br />nearly 100% (intravenous)<ref name="pmid35361640">{{cite journal | vauthors = Luo A, Liu X, Hu Q, Yang M, Jiang H, Liu W | title = Efficacy of ''N''-acetylcysteine on idiopathic or postinfective non-cystic fibrosis bronchiectasis: a systematic review and meta-analysis protocol | journal = BMJ Open | volume = 12 | issue = 3 | article-number = e053625 | date = March 2022 | pmid = 35361640 | pmc = 8971804 | doi = 10.1136/bmjopen-2021-053625 }}</ref>
| protein_bound = 50 to 83%<ref name="The American Society of Health-System Pharmacists"/>
| metabolism = [[Liver]]<ref name="The American Society of Health-System Pharmacists"/>
| metabolites = 
| onset = 
| elimination_half-life = 5.6 hours<ref name="Acetadote FDA label">{{cite web | title=Acetadote- acetylcysteine injection, solution | website=DailyMed | date=1 October 2021 | url=https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=472f158a-5ab9-4308-8e49-1116e6ea3d39 | access-date=29 December 2022 | archive-date=30 December 2022 | archive-url=https://web.archive.org/web/20221230073232/https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=472f158a-5ab9-4308-8e49-1116e6ea3d39 | url-status=live }}</ref>
| duration_of_action = 
| excretion = Kidney (30%),<ref name="The American Society of Health-System Pharmacists"/> faecal (3%)

<!-- Identifiers -->
| CAS_number = 616-91-1
| CAS_supplemental = 
| PubChem = 12035
| IUPHAR_ligand = 
| DrugBank = DB06151
| ChemSpiderID = 11540
| UNII = WYQ7N0BPYC
| KEGG = D00221
| ChEBI = 28939
| ChEMBL = 600
| NIAID_ChemDB = 
| PDB_ligand = 
| synonyms = ''N''-acetylcysteine; ''N''-acetyl-<small>L</small>-cysteine; NALC; NAC

<!-- Chemical and physical data -->
| IUPAC_name = (2''R'')-2-acetamido-3-sulfanylpropanoic acid<ref name="PubChem-2005">{{cite web|title=<small>L</small>-Cysteine, ''N''-acetyl- — Compound Summary|url=https://pubchem.ncbi.nlm.nih.gov/compound/581|work=PubChem|publisher=National Center for Biotechnology Information, U.S. National Library of Medicine |access-date=9 January 2012|date=25 March 2005|at=Identification|url-status=live|archive-url=https://web.archive.org/web/20140112235508/http://pubchem.ncbi.nlm.nih.gov/summary/summary.cgi?cid=581|archive-date=12 January 2014}}</ref>
| C = 5
| H = 9
| N = 1
| O = 3
| S = 1
| SMILES = C/C(=N/[C@@H](CS)C(=O)O)/O
| StdInChI_comment = 
| StdInChI = 1S/C5H9NO3S/c1-3(7)6-4(2-10)5(8)9/h4,10H,2H2,1H3,(H,6,7)(H,8,9)/t4-/m0/s1
| StdInChIKey = PWKSKIMOESPYIA-BYPYZUCNSA-N
| density = 
| density_notes = 
| melting_point = 109
| melting_high = 110
| melting_notes = <ref name="Sigma-2014"/>
| boiling_point = 
| boiling_notes = 
| solubility = 
| sol_units = 
| specific_rotation = +5° (c = 3% in water)<ref name="Sigma-2014"/>
}}

<!-- Definition and uses -->
'''Acetylcysteine''' or  '''''N''-acetylcysteine''' ('''NAC'''; not to be confused with [[Acetylcarnosine|''N''-acetylcarnosine]], which is also abbreviated NAC) is a [[mucolytic]] that is used to treat [[paracetamol overdose|paracetamol (acetaminophen) overdose]] and to loosen thick [[mucus]] in individuals with chronic bronchopulmonary disorders, such as [[pneumonia]] and [[bronchitis]].<ref name="The American Society of Health-System Pharmacists">{{cite web|title=Acetylcysteine|url=https://www.drugs.com/monograph/acetylcysteine.html|publisher=The American Society of Health-System Pharmacists|access-date=22 August 2015|url-status=live|archive-url=https://web.archive.org/web/20150923231013/http://www.drugs.com/monograph/acetylcysteine.html|archive-date=23 September 2015}}</ref><ref name="Sandoz">{{cite web|title=ACC® 600 ORAL POWDER|url=https://my-sandoz-com-za-en.cms.sandoz.com/sites/default/files/2023-04/ACC%20600%20PI.pdf|publisher=[[Sandoz]]|access-date=12 June 2025|url-status=bot: unknown|quote=Acetylcysteine is a mucolytic agent that reduces the viscosity of non-infected bronchial secretions probably by the splitting of disulphide bonds in mucoproteins.|archive-date=12 June 2025|archive-url=https://web.archive.org/web/20250612092745/https://my-sandoz-com-za-en.cms.sandoz.com/sites/default/files/2023-04/ACC%20600%20PI.pdf}}</ref> It has been used to treat [[bezoars|lactobezoar]] in infants. It can be taken [[Intravenous therapy|intravenously]], [[oral administration|orally]] (swallowed by mouth), or [[Inhalation administration|inhaled as a mist]] by use of a [[nebulizer]].<ref name="The American Society of Health-System Pharmacists"/><ref name="f779">{{cite web | title=Acetylcysteine Oral Inhalation: MedlinePlus Drug Information | website=MedlinePlus | url=https://medlineplus.gov/druginfo/meds/a615021.html | access-date=22 February 2025 | quote=Acetylcysteine comes as a solution (liquid) and concentrated solution to inhale by mouth using a nebulizer ...}}</ref> It is also sometimes used as a [[dietary supplement]].<ref name="Talbott-2012">{{cite book|vauthors=Talbott SM|title=A Guide to Understanding Dietary Supplements|date=2012|publisher=Routledge|isbn=978-1-136-80570-7|page=469|url=https://books.google.com/books?id=9ZZrW_j9XrcC&pg=PA469|url-status=live|archive-url=https://web.archive.org/web/20170908143219/https://books.google.com/books?id=9ZZrW_j9XrcC&pg=PA469|archive-date=8 September 2017}}</ref><ref name="University of Maryland Medical Center">{{cite web|title=Cysteine|url=http://www.umm.edu/health/medical/altmed/supplement/cysteine|website=University of Maryland Medical Center|access-date=23 June 2017|url-status=live|archive-url=https://web.archive.org/web/20170701184417/http://www.umm.edu/health/medical/altmed/supplement/cysteine|archive-date=1 July 2017}}</ref>

<!-- Side effects and mechanism -->
Common side effects include nausea and vomiting when taken orally.<ref name="The American Society of Health-System Pharmacists"/> The skin may occasionally become [[erythema|red]] and [[itch]]y with any route of administration.<ref name="The American Society of Health-System Pharmacists"/> A non-immune type of [[anaphylaxis]] may also occur.<ref name="The American Society of Health-System Pharmacists"/> It appears to be safe in pregnancy.<ref name="The American Society of Health-System Pharmacists"/> For paracetamol overdose, it works by increasing the level of [[glutathione]], an antioxidant that can neutralize the toxic breakdown products of paracetamol.<ref name="The American Society of Health-System Pharmacists"/> When inhaled, it acts as a [[Mucokinetics|mucolytic]] by decreasing the thickness of mucus.<ref name="pmid18044098">{{cite journal | vauthors = Sadowska AM, Verbraecken J, Darquennes K, De Backer WA | title = Role of ''N''-acetylcysteine in the management of COPD | journal = International Journal of Chronic Obstructive Pulmonary Disease | volume = 1 | issue = 4 | pages = 425–434 | date = December 2006 | pmid = 18044098 | pmc = 2707813 | doi = 10.2147/copd.2006.1.4.425 | doi-access = free }}</ref>

<!-- History, society and culture -->
Acetylcysteine was initially patented in 1960 and came into medical use in 1968.<ref name="Fischer-2006">{{cite book | vauthors = Fischer J, Ganellin CR | title = Analogue-Based Drug Discovery | date = 2006 | publisher = Wiley-VCH | location = Weinheim | isbn = 978-3-527-60749-5 | page = 544 | url = https://books.google.com/books?id=FjKfqkaKkAAC&pg=PA544 | url-status = live | archive-url = https://web.archive.org/web/20170908143219/https://books.google.com/books?id=FjKfqkaKkAAC&pg=PA544 | archive-date = 8 September 2017 }}</ref><ref name="US3091569A-1963">{{Cite patent|number=US3091569A|title=Mucolytic-nu-acylated sulfhydryl compositions and process for treating animal mucus|gdate=28 May 1963|inventor = Sheffner AL |url=https://patents.google.com/patent/US3091569A/en}} {{Webarchive|url=https://web.archive.org/web/20240806002723/https://patents.google.com/patent/US3091569A/en |date=6 August 2024 }}</ref><ref name="US patent 3091569-1963">{{cite patent |country=US |number=3091569 |status=patent |title=Mucolytic-''N''-acylated sulfhydryl compositions and process for treating animal mucus |pubdate=28 May 1963 |gdate=28 May 1963 |fdate=26 August 1960 |pridate=26 August 1960 |inventor = Sheffner AL |assign1=Mead Johnson & Co |url=https://worldwide.espacenet.com/publicationDetails/biblio?II=2&ND=3&adjacent=true&locale=en_EP&FT=D&date=19630528&CC=US&NR=3091569A&KC=A }} {{Webarchive|url=https://web.archive.org/web/20240630120932/https://worldwide.espacenet.com/publicationDetails/biblio?II=2&ND=3&adjacent=true&locale=en_EP&FT=D&date=19630528&CC=US&NR=3091569A&KC=A |date=30 June 2024 }}</ref> It is on the [[WHO Model List of Essential Medicines|World Health Organization's List of Essential Medicines]].<ref name="WHO23rd">{{cite book | vauthors = ((World Health Organization)) | title = The selection and use of essential medicines 2023: web annex A: World Health Organization model list of essential medicines: 23rd list (2023) | year = 2023 | hdl = 10665/371090 | author-link = World Health Organization | publisher = World Health Organization | location = Geneva | id = WHO/MHP/HPS/EML/2023.02 | hdl-access=free }}</ref> It is available as a [[generic medication]].<ref name="Baker-2014">{{cite book | vauthors = Baker E | title = Top 100 Drugs: Clinical pharmacology and practical prescribing | date = 2014 | publisher = Elsevier Health Sciences | isbn = 978-0-7020-5515-7 | entry = Acetylcysteine | url = https://books.google.com/books?id=oeYjAwAAQBAJ&pg=PT44 | url-status = live | archive-url = https://web.archive.org/web/20170908143223/https://books.google.com/books?id=oeYjAwAAQBAJ&pg=PT44 | archive-date = 8 September 2017 }}</ref>

<!-- Storage -->
The sulfur-containing amino acids [[cysteine]] and [[methionine]] are more easily oxidized than the other amino acids.<ref name="pmid29445748">{{cite journal | vauthors = Bin P, Huang R, Zhou X | title = Oxidation Resistance of the Sulfur Amino Acids: Methionine and Cysteine | journal = BioMed Research International | volume = 2017 | article-number = 9584932 | date = 2017 | pmid = 29445748 | pmc = 5763110 | doi = 10.1155/2017/9584932 | title-link = doi | doi-access = free }}</ref><ref name="BCLee">{{cite journal | vauthors = Lee BC, Dikiy A, Kim HY, Gladyshev VN | title = Functions and evolution of selenoprotein methionine sulfoxide reductases | journal = Biochimica et Biophysica Acta (BBA) - General Subjects | volume = 1790 | issue = 11 | pages = 1471–1477 | date = November 2009 | pmid = 19406207 | pmc = 3062201 | doi = 10.1016/j.bbagen.2009.04.014 }}</ref>

== Uses ==
=== Medical uses ===

====Paracetamol overdose antidote====
{{Main|Paracetamol poisoning}}
Intravenous and oral formulations of acetylcysteine are available for the treatment of [[paracetamol]] (acetaminophen) overdose.<ref name="pmid23687539">{{cite journal | vauthors = Green JL, Heard KJ, Reynolds KM, Albert D | title = Oral and Intravenous Acetylcysteine for Treatment of Acetaminophen Toxicity: A Systematic Review and Meta-analysis | journal = The Western Journal of Emergency Medicine | volume = 14 | issue = 3 | pages = 218–226 | date = May 2013 | pmid = 23687539 | pmc = 3656701 | doi = 10.5811/westjem.2012.4.6885 }}</ref> When paracetamol is taken in large quantities, a toxic minor metabolite called ''N''-acetyl-''p''-benzoquinone imine ([[NAPQI]]) accumulates within the body. It is normally [[Xenobiotic metabolism#Phase II – conjugation|conjugated]] by [[glutathione]], but when taken in excess, the body's glutathione reserves are not sufficient to deactivate the toxic NAPQI. This metabolite is then free to react with key hepatic enzymes, thereby damaging [[hepatocyte|liver cells]]. This may lead to severe liver damage and even death by [[acute liver failure]].

In the treatment of paracetamol (acetaminophen) overdose, acetylcysteine acts to maintain or replenish depleted glutathione reserves in the liver and enhance non-toxic metabolism of acetaminophen.<ref name="Acetadote FDA label" /> These actions serve to protect liver cells from NAPQI toxicity. It is most effective in preventing or lessening hepatic injury when administered within 8–10 hours after overdose.<ref name="Acetadote FDA label" /> Research suggests that the rate of liver toxicity is approximately 3% when acetylcysteine is administered within 10 hours of overdose.<ref name="pmid23687539" />

Although IV and oral acetylcysteine are equally effective for this indication, oral administration is generally poorly tolerated due to the higher dosing required to overcome its low oral [[bioavailability]],<ref name="pmid3803419">{{cite journal | vauthors = Borgström L, Kågedal B, Paulsen O | title = Pharmacokinetics of ''N''-acetylcysteine in man | journal = European Journal of Clinical Pharmacology | volume = 31 | issue = 2 | pages = 217–222 | date = 1986 | pmid = 3803419 | doi = 10.1007/bf00606662 | s2cid = 41004554 }}</ref> its foul taste and odor, and a higher incidence of [[adverse drug reaction|adverse effect]]s when taken orally, particularly nausea and vomiting. Prior pharmacokinetic studies of acetylcysteine did not consider [[acetylation]] as a reason for the low bioavailability of acetylcysteine.<ref name="pmid17371789">{{cite journal | vauthors = Dilger RN, Baker DH | title = Oral ''N''-acetyl-<small>L</small>-cysteine is a safe and effective precursor of cysteine | journal = Journal of Animal Science | volume = 85 | issue = 7 | pages = 1712–1718 | date = July 2007 | pmid = 17371789 | doi = 10.2527/jas.2006-835 }}</ref> Oral acetylcysteine is identical in bioavailability to cysteine precursors.<ref name="pmid17371789"/> However, 3% to 6% of people given intravenous acetylcysteine show a severe, [[anaphylaxis]]-like allergic reaction, which may include extreme breathing difficulty (due to [[bronchospasm]]), [[hypotension|a decrease in blood pressure]], rash, [[angioedema]], and sometimes also nausea and vomiting.<ref name="pmid16990628">{{cite journal | vauthors = Kanter MZ | title = Comparison of oral and i.v. acetylcysteine in the treatment of acetaminophen poisoning | journal = American Journal of Health-System Pharmacy | volume = 63 | issue = 19 | pages = 1821–1827 | date = October 2006 | pmid = 16990628 | doi = 10.2146/ajhp060050 | s2cid = 9209528 }}</ref> Repeated doses of intravenous acetylcysteine will cause these allergic reactions to progressively worsen in these people.

Several studies have found this anaphylaxis-like reaction to occur more often in people given intravenous acetylcysteine despite serum levels of paracetamol not high enough to be considered toxic.<ref name="pmid2716644">{{cite journal | vauthors = Dawson AH, Henry DA, McEwen J | title = Adverse reactions to ''N''-acetylcysteine during treatment for paracetamol poisoning | journal = The Medical Journal of Australia | volume = 150 | issue = 6 | pages = 329–331 | date = March 1989 | pmid = 2716644 | doi = 10.5694/j.1326-5377.1989.tb136496.x | s2cid = 40296724 }}</ref><ref name="pmid9624310">{{cite journal | vauthors = Bailey B, McGuigan MA | title = Management of anaphylactoid reactions to intravenous ''N''-acetylcysteine | journal = Annals of Emergency Medicine | volume = 31 | issue = 6 | pages = 710–715 | date = June 1998 | pmid = 9624310 | doi = 10.1016/S0196-0644(98)70229-X }}</ref><ref name="pmid11167669">{{cite journal | vauthors = Schmidt LE, Dalhoff K | title = Risk factors in the development of adverse reactions to ''N''-acetylcysteine in patients with paracetamol poisoning | journal = British Journal of Clinical Pharmacology | volume = 51 | issue = 1 | pages = 87–91 | date = January 2001 | pmid = 11167669 | pmc = 2014432 | doi = 10.1046/j.1365-2125.2001.01305.x }}</ref><ref name="pmid14700565">{{cite journal | vauthors = Lynch RM, Robertson R | title = Anaphylactoid reactions to intravenous ''N''-acetylcysteine: a prospective case controlled study | journal = Accident and Emergency Nursing | volume = 12 | issue = 1 | pages = 10–15 | date = January 2004 | pmid = 14700565 | doi = 10.1016/j.aaen.2003.07.001 }}</ref>

====Mucolytic agent====
Acetylcysteine exhibits [[mucolytic]] properties, meaning it reduces the viscosity and adhesiveness of [[mucus]]. This therapeutic effect is achieved through the cleavage of [[disulfide bond]]s<ref name="pmid34171332">{{cite journal | vauthors = Pedre B, Barayeu U, Ezeriņa D, Dick TP | title = The mechanism of action of ''N''-acetylcysteine (NAC): The emerging role of H<sub>2</sub>S and sulfane sulfur species | journal = Pharmacology & Therapeutics | volume = 228 | article-number = 107916 | date = December 2021 | pmid = 34171332 | doi = 10.1016/j.pharmthera.2021.107916 | doi-access = free }}</ref> within [[mucoprotein]]s (strongly cross-linked [[mucin]]s),<ref name="pmid33380301">{{cite journal | vauthors = Raghu G, Berk M, Campochiaro PA, Jaeschke H, Marenzi G, Richeldi L, Wen FQ, Nicoletti F, Calverley PM | title = The Multifaceted Therapeutic Role of ''N''-acetylcysteine (NAC) in Disorders Characterized by Oxidative Stress | journal = Current Neuropharmacology | volume = 19 | issue = 8 | pages = 1202–1224 | date = 2021 | pmid = 33380301 | pmc = 8719286 | doi = 10.2174/1570159X19666201230144109 }}</ref> thereby decreasing the mucus viscosity and facilitating its clearance from the respiratory tract. This mechanism is particularly beneficial in conditions characterized by excessive or thickened mucus,<ref name="pmid34221501">{{cite journal | vauthors = Schwalfenberg GK | title = ''N''-acetylcysteine: A Review of Clinical Usefulness (an Old Drug with New Tricks) | journal = Journal of Nutrition and Metabolism | volume = 2021 | article-number = 9949453 | date = 2021 | pmid = 34221501 | pmc = 8211525 | doi = 10.1155/2021/9949453 | doi-access = free }}</ref> such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, rhinitis or sinusitis.<ref name="doi1945892421994999">{{cite journal | vauthors = Saltagi MZ, Comer BT, Hughes S, Ting JY, Higgins TS | title = Management of Recurrent Acute Rhinosinusitis: A Systematic Review | journal = American Journal of Rhinology & Allergy | volume = 35 | issue = 6 | pages = 902–909 | date = November 2021 | pmid = 33622038 | doi = 10.1177/1945892421994999 }}</ref> Acetylcysteine can be administered as a part of a complex molecule, [[thiamphenicol glycinate acetylcysteine]], which also contains [[thiamphenicol]], an antibiotic.<ref name="pmid17880774">{{cite journal | vauthors = Serra A, Schito GC, Nicoletti G, Fadda G | title = A therapeutic approach in the treatment of infections of the upper airways: thiamphenicol glycinate acetylcysteinate in sequential treatment (systemic-inhalatory route) | journal = International Journal of Immunopathology and Pharmacology | volume = 20 | issue = 3 | pages = 607–617 | date = 2007 | pmid = 17880774 | doi = 10.1177/039463200702000319 }}</ref>

=====Lungs=====
Inhaled acetylcysteine has been used for [[mucolytic]] therapy in addition to other therapies in respiratory conditions with excessive and/or thick mucus production. It is also used post-operatively, as a diagnostic aid, and in [[tracheotomy]] care. It may be considered ineffective in [[cystic fibrosis]].<ref name="Rossi-2006">{{cite book | veditors = Rossi S | title = [[Australian Medicines Handbook]] | date = 2006 | location = Adelaide | publisher = Australian Medicines Handbook }}</ref> A 2013 Cochrane review in cystic fibrosis found no evidence of benefit.<ref name="pmid23852992">{{cite journal | vauthors = Tam J, Nash EF, Ratjen F, Tullis E, Stephenson A | title = Nebulized and oral thiol derivatives for pulmonary disease in cystic fibrosis | journal = The Cochrane Database of Systematic Reviews | volume = 2013 | issue = 7 | article-number = CD007168 | date = July 2013 | pmid = 23852992 | pmc = 8078644 | doi = 10.1002/14651858.CD007168.pub3 | doi-access = free | title-link = doi }}</ref>

Acetylcysteine is used in the treatment of [[obstructive lung disease]] as an adjuvant treatment.<ref name="pmid10743980">{{cite journal | vauthors = Grandjean EM, Berthet P, Ruffmann R, Leuenberger P | title = Efficacy of oral long-term ''N''-acetylcysteine in chronic bronchopulmonary disease: a meta-analysis of published double-blind, placebo-controlled clinical trials | journal = Clinical Therapeutics | volume = 22 | issue = 2 | pages = 209–221 | date = February 2000 | pmid = 10743980 | doi = 10.1016/S0149-2918(00)88479-9 }}</ref><ref name="pmid10968500">{{cite journal | vauthors = Stey C, Steurer J, Bachmann S, Medici TC, Tramèr MR | title = The effect of oral ''N''-acetylcysteine in chronic bronchitis: a quantitative systematic review | journal = The European Respiratory Journal | volume = 16 | issue = 2 | pages = 253–262 | date = August 2000 | pmid = 10968500 | doi = 10.1034/j.1399-3003.2000.16b12.x | title-link = doi | doi-access = free | citeseerx = 10.1.1.516.9510 }}</ref><ref name="pmid11375228">{{cite journal | vauthors = Poole PJ, Black PN | title = Oral mucolytic drugs for exacerbations of chronic obstructive pulmonary disease: systematic review | journal = BMJ | volume = 322 | issue = 7297 | pages = 1271–1274 | date = May 2001 | pmid = 11375228 | pmc = 31920 | doi = 10.1136/bmj.322.7297.1271 }}</ref>

===Other uses===
Acetylcysteine has been used to [[Chelation|complex]] [[palladium]], to help it dissolve in water. This helps to remove palladium from drugs or precursors synthesized by palladium-catalyzed [[coupling reaction]]s.<ref name="Garrett-2004">{{cite journal | vauthors = Garrett CE, Prasad K |title=The Art of Meeting Palladium Specifications in Active Pharmaceutical Ingredients Produced by Pd-Catalyzed Reactions |journal=Advanced Synthesis & Catalysis |volume=346 |pages=889–900 |year=2004 |doi=10.1002/adsc.200404071 |issue=8|s2cid=94929244 }}</ref> ''N''-acetylcysteine can be used to protect the liver.<ref name="pmid31643176">{{citation |title=Acetylcysteine |url=https://www.ncbi.nlm.nih.gov/books/NBK547852/ |website=livertox.nih.gov |date=2012 |pmid=31643176 |access-date=26 April 2019 |archive-date=25 April 2019 |archive-url=https://web.archive.org/web/20190425234436/https://livertox.nih.gov/Acetylcysteine.htm |url-status=live }}</ref>

====Microbiological use====
Acetylcysteine can be used in Petroff's method of liquefaction and decontamination of [[sputum]], in preparation for recovery of [[mycobacterium]].<ref name=Bujitels>{{cite journal | vauthors = Buijtels PC, Petit PL | title = Comparison of NaOH-''N''-acetyl cysteine and sulfuric acid decontamination methods for recovery of mycobacteria from clinical specimens | journal = Journal of Microbiological Methods | volume = 62 | issue = 1 | pages = 83–88 | date = July 2005 | pmid = 15823396 | doi = 10.1016/j.mimet.2005.01.010 }}</ref> It also displays significant antiviral activity against [[Influenzavirus A|influenza A viruses]].<ref name="pmid19732754">{{cite journal | vauthors = Geiler J, Michaelis M, Naczk P, Leutz A, Langer K, Doerr HW, Cinatl J | title = ''N''-acetyl-L-cysteine (NAC) inhibits virus replication and expression of pro-inflammatory molecules in A549 cells infected with highly pathogenic H5N1 influenza A virus | journal = Biochemical Pharmacology | volume = 79 | issue = 3 | pages = 413–420 | date = February 2010 | pmid = 19732754 | doi = 10.1016/j.bcp.2009.08.025 | url = https://hal.archives-ouvertes.fr/hal-00538093/file/PEER_stage2_10.1016%252Fj.bcp.2009.08.025.pdf | access-date = 14 October 2021 | url-status = live | archive-url = https://web.archive.org/web/20240806002728/https://hal.archives-ouvertes.fr/hal-00538093/file/PEER_stage2_10.1016%252Fj.bcp.2009.08.025.pdf | archive-date = 6 August 2024 }}</ref>

Acetylcysteine has [[bactericidal]] properties and breaks down bacterial [[biofilm]]s of clinically relevant pathogens including ''[[Pseudomonas aeruginosa]]'', ''[[Staphylococcus aureus]]'', ''[[Enterococcus faecalis]]'', ''[[Enterobacter cloacae]]'', ''[[Staphylococcus epidermidis]]'', and ''[[Klebsiella pneumoniae]]''.<ref name="pmid22094553">{{cite journal | vauthors = Aslam S, Darouiche RO | title = Role of antibiofilm-antimicrobial agents in controlling device-related infections | journal = The International Journal of Artificial Organs | volume = 34 | issue = 9 | pages = 752–758 | date = September 2011 | pmid = 22094553 | pmc = 3251652 | doi = 10.5301/ijao.5000024 }}</ref>

==Side effects==
{{redirect|SNOAC|the gene|snoaC{{!}}''sno''aC}}

The most commonly reported adverse effects for I.V. formulations of acetylcysteine are rash, [[urticaria]], and [[pruritus|itchiness]].<ref name="Acetadote FDA label" />

Adverse effects for inhalational formulations of acetylcysteine include nausea, vomiting, [[stomatitis]], fever, [[rhinorrhea]], drowsiness, clamminess, chest tightness, and bronchoconstriction. Although infrequent, bronchospasm has been reported to occur unpredictably in some patients.<ref name="Mucomyst Package Insert-2014">{{cite web|title=Mucomyst Package Insert|url=https://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=d2dc24f3-3ad7-4c6c-8e9f-7202d9a146f7|access-date=20 April 2014|url-status=live|archive-url=https://web.archive.org/web/20140421050640/http://dailymed.nlm.nih.gov/dailymed/lookup.cfm?setid=d2dc24f3-3ad7-4c6c-8e9f-7202d9a146f7|archive-date=21 April 2014}}</ref>

Adverse effects for oral formulations of acetylcysteine have been reported to include nausea, vomiting, rash, and fever.<ref name="Mucomyst Package Insert-2014"/>

Large doses in a mouse model showed that acetylcysteine could potentially cause damage to the [[heart]] and [[lungs]].<ref name="pmid17786245">{{cite journal | vauthors = Palmer LA, Doctor A, Chhabra P, Sheram ML, Laubach VE, Karlinsey MZ, Forbes MS, Macdonald T, Gaston B | title = S-nitrosothiols signal hypoxia-mimetic vascular pathology | journal = The Journal of Clinical Investigation | volume = 117 | issue = 9 | pages = 2592–2601 | date = September 2007 | pmid = 17786245 | pmc = 1952618 | doi = 10.1172/JCI29444 }}</ref> They found that acetylcysteine was [[drug metabolism|metabolized]] to ''S''-nitroso-''N''-acetylcysteine ('''{{vanchor|SNOAC}}'''), which increased [[blood pressure]] in the lungs and [[right ventricle]] of the heart ([[pulmonary artery hypertension]]) in [[mice]] treated with acetylcysteine. The effect was similar to that observed following a 3-week exposure to an oxygen-deprived environment (chronic [[hypoxia (medical)|hypoxia]]). The authors also found that SNOAC induced a hypoxia-like response in the [[gene expression|expression]] of several important [[gene]]s both ''[[in vitro]]'' and ''[[in vivo]]''. The implications of these findings for long-term treatment with acetylcysteine have not yet been investigated. The dose used by Palmer and colleagues was dramatically higher than that used in humans, the equivalent of about 20 grams per day.<ref name="pmid17786245"/> In humans, much lower dosages (600&nbsp;mg per day) have been observed to counteract some age-related decline in the [[hypoxic ventilatory response]] as tested by inducing prolonged [[hypoxia (medical)|hypoxia]].<ref name="pmid11861267">{{cite journal | vauthors = Hildebrandt W, Alexander S, Bärtsch P, Dröge W | title = Effect of ''N''-acetyl-cysteine on the hypoxic ventilatory response and erythropoietin production: linkage between plasma thiol redox state and O(2) chemosensitivity | journal = Blood | volume = 99 | issue = 5 | pages = 1552–1555 | date = March 2002 | pmid = 11861267 | doi = 10.1182/blood.V99.5.1552 | s2cid = 24375953 | title-link = doi | doi-access = free }}</ref>

Although ''N''-acetylcysteine prevented liver damage in mice when taken before alcohol, when taken four hours after alcohol it made liver damage worse in a dose-dependent fashion.<ref name="Wang_2006">{{cite journal | vauthors = Wang AL, Wang JP, Wang H, Chen YH, Zhao L, Wang LS, Wei W, Xu DX | title = A dual effect of ''N''-acetylcysteine on acute ethanol-induced liver damage in mice | journal = Hepatology Research | volume = 34 | issue = 3 | pages = 199–206 | date = March 2006 | pmid = 16439183 | doi = 10.1016/j.hepres.2005.12.005 }}</ref>

==Pharmacology==

===Pharmacodynamics===
Acetylcysteine serves as a [[prodrug]] to [[L-cysteine|<small>L</small>-cysteine]], a precursor to the biologic antioxidant [[glutathione]]. Hence administration of acetylcysteine replenishes glutathione stores.<ref name=TGA>{{cite web|title=Product Information: Aceradote Concentrated Injection|work=TGA eBusiness Services|publisher=Phebra Pty Ltd|url=https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-03960-3|format=PDF|date=16 January 2013|access-date=8 November 2013|url-status=live|archive-url=https://web.archive.org/web/20170908143219/https://www.ebs.tga.gov.au/ebs/picmi/picmirepository.nsf/pdf?OpenAgent&id=CP-2010-PI-03960-3|archive-date=8 September 2017}}</ref>
* Glutathione, along with [[oxidized glutathione]] (GSSG) and [[S-nitrosoglutathione|''S''-nitrosoglutathione]] (GSNO), have been found to bind to the [[glutamate]] recognition site of the [[NMDA receptor|NMDA]] and [[AMPA receptor]]s (via their γ-glutamyl moieties), and may be [[endogenous]] [[neuromodulator]]s.<ref name="SteulletNeijt2006">{{cite journal | vauthors = Steullet P, Neijt HC, Cuénod M, Do KQ | title = Synaptic plasticity impairment and hypofunction of NMDA receptors induced by glutathione deficit: relevance to schizophrenia | journal = Neuroscience | volume = 137 | issue = 3 | pages = 807–819 | date = February 2006 | pmid = 16330153 | doi = 10.1016/j.neuroscience.2005.10.014 | s2cid = 1417873 }}</ref><ref name="VargaJenei1997">{{cite journal | vauthors = Varga V, Jenei Z, Janáky R, Saransaari P, Oja SS | title = Glutathione is an endogenous ligand of rat brain N-methyl-D-aspartate (NMDA) and 2-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptors | journal = Neurochemical Research | volume = 22 | issue = 9 | pages = 1165–1171 | date = September 1997 | pmid = 9251108 | doi = 10.1023/A:1027377605054 | s2cid = 24024090 }}</ref> At [[millimolar]] concentrations, they may also modulate the redox state of the NMDA receptor complex.<ref name="VargaJenei1997" /> In addition, glutathione has been found to bind to and activate [[ionotropic receptor]]s that are different from any other [[excitatory amino acid receptor]], and which may constitute ''glutathione receptors'', potentially making it a [[neurotransmitter]].<ref name="pmid10812215">{{cite journal | vauthors = Oja SS, Janáky R, Varga V, Saransaari P | title = Modulation of glutamate receptor functions by glutathione | journal = Neurochemistry International | volume = 37 | issue = 2–3 | pages = 299–306 | year = 2000 | pmid = 10812215 | doi = 10.1016/S0197-0186(00)00031-0 | s2cid = 44380765 }}</ref> As such, since ''N''-acetylcysteine is a prodrug of glutathione, it may modulate all of the aforementioned receptors as well.
* Glutathione also modulates the [[NMDA receptor]] by acting at the redox site.<ref name="pmid23369637"/><ref name="DOI2008">{{cite journal | vauthors = Lavoie S, Murray MM, Deppen P, Knyazeva MG, Berk M, Boulat O, Bovet P, Bush AI, Conus P, Copolov D, Fornari E, Meuli R, Solida A, Vianin P, Cuénod M, Buclin T, Do KQ | title = Glutathione precursor, ''N''-acetyl-cysteine, improves mismatch negativity in schizophrenia patients | journal = Neuropsychopharmacology | volume = 33 | issue = 9 | pages = 2187–2199 | date = August 2008 | pmid = 18004285 | doi = 10.1038/sj.npp.1301624 | hdl-access = free | title-link = doi | doi-access = free | hdl = 10536/DRO/DU:30071388 }}</ref>

Acetylcysteine also serves as a precursor to [[cystine]], which in turn serves as a substrate for the [[SLC7A11|cystine-glutamate antiporter]] on [[astrocytes]]; hence there is increasing glutamate release into the extracellular space. This glutamate in turn acts on [[metabotropic glutamate receptor|mGluR<sub>2/3</sub>]] receptors, and at higher doses of acetylcysteine, [[metabotropic glutamate receptor 5|mGluR<sub>5</sub>]].<ref name="BM2008">{{cite journal | vauthors = Dodd S, Dean O, Copolov DL, Malhi GS, Berk M | title = ''N''-acetylcysteine for antioxidant therapy: pharmacology and clinical utility | journal = Expert Opinion on Biological Therapy | volume = 8 | issue = 12 | pages = 1955–1962 | date = December 2008 | pmid = 18990082 | doi = 10.1517/14728220802517901 | s2cid = 74736842 }}</ref><ref name="NAc2012">{{cite journal | vauthors = Kupchik YM, Moussawi K, Tang XC, Wang X, Kalivas BC, Kolokithas R, Ogburn KB, Kalivas PW | title = The effect of ''N''-acetylcysteine in the nucleus accumbens on neurotransmission and relapse to cocaine | journal = Biological Psychiatry | volume = 71 | issue = 11 | pages = 978–986 | date = June 2012 | pmid = 22137594 | pmc = 3340445 | doi = 10.1016/j.biopsych.2011.10.024 }}</ref> Acetylcysteine may have other biological functions in the brain, such as the modulation of dopamine release and the reduction in inflammatory cytokine formation possibly via inhibiting [[NF-κB]] and modulating cytokine synthesis.<ref name="pmid23369637" /> These properties, along with the reduction of oxidative stress and the re-establishment of glutamatergic balance, would lead to an increase in growth factors, such as brain-derived neurotrophic factor ([[BDNF]]), and the regulation of neuronal cell death through B-cell lymphoma 2 expression ([[Bcl-2|BLC-2]]).<ref name="pmid21118657" />

As mentioned before, actylcysteine clears mucus by opening disulfide bonds.<ref name="pmid34171332"/>

===Pharmacokinetics===
The oral bioavailability of acetylcysteine is relatively low due to extensive first-pass metabolism in the gut wall and liver. It ranges between 6% and 10%.

Intravenous administration of acetylcysteine bypasses the first-pass metabolism, resulting in higher bioavailability compared to oral administration. Intravenous administration of acetylcysteine ensures nearly 100% bioavailability as it directly enters the bloodstream.

Acetylcysteine is extensively liver metabolized, CYP450 minimal, urine excretion is 22–30% with a [[half-life]] of 5.6 hours in adults and 11 hours in newborns.{{medical citation needed|date=August 2024}}

Acetylcysteine is the ''N''-[[acetyl]] derivative of the amino acid <small>L</small>-cysteine, and is a precursor in the formation of the antioxidant [[glutathione]] in the body. The [[thiol]] (sulfhydryl) group confers antioxidant effects and is able to [[Redox|reduce]] [[free radical]]s.

==Chemistry==
Pure acetylcysteine is in a solid state at room temperature, appearing as a white crystalline powder or granules.<ref name="pmid33638319">{{cite journal| doi=10.1515/jbcpp-2020-0099 | title=An insight on safety, efficacy, and molecular docking study reports of N-acetylcysteine and its compound formulations | date=2022 | journal=Journal of Basic and Clinical Physiology and Pharmacology | volume=33 | issue=3 | pages=223–233 | pmid=33638319 | vauthors = Rind L, Ahmad M, Khan MI, Badruddeen, Akhtar J, Ahmad U, Yadav C, Owais M }}</ref> The solid form of acetylcysteine is stable under normal conditions, but it can undergo oxidation if exposed to air or moisture over time, leading to the formation of its dimeric form, diacetylcysteine, which can have different properties.{{scicn|date=December 2025}} Acetylcysteine is highly hygroscopic, i.e., it absorbs moisture if exposed to open air.<ref name="pmid33638319"/>

Acetylcysteine can sometimes appear as a light yellow cast powder instead of pure white due to oxidation. The sulfur-containing amino acids, like cysteine, are more easily oxidized than other amino acids. When exposed to air or moisture, acetylcysteine can oxidize, leading to a slight yellowish tint.<ref name="pmid33638319"/>

Acetylcysteine in a form of a white or white with light yellow cast powder has a [[pKa|p''K''<sub>a</sub>]] of 9.5 at 30&nbsp;°C.<ref name="Sigma-2014">{{cite web|title=''N''-Acetyl-<small>L</small>-cysteine Product Information |url=https://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Product_Information_Sheet/a7250pis.pdf |website=Sigma |publisher=Sigma-Aldrich |access-date=9 November 2014 |archive-url=https://web.archive.org/web/20140611120709/http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma-Aldrich/Product_Information_Sheet/a7250pis.pdf |archive-date=11 June 2014 }}</ref>

''N''-acetyl-<small>L</small>-cysteine is soluble in water and alcohol, and practically insoluble in chloroform and ether.<ref name="PubChem-2016">{{cite web|title=''N''-Acetyl-<small>L</small>-cysteine {{pipe}} C<sub>5</sub>H<sub>9</sub>NO<sub>3</sub>S|work = PubChem |publisher=National Center for Biotechnology Information, U.S. National Library of Medicine |url=https://pubchem.ncbi.nlm.nih.gov/compound/''N''-acetyl-L-cysteine#section=Chemical-and-Physical-Properties|access-date=22 July 2016|archive-url=https://web.archive.org/web/20160816171151/https://pubchem.ncbi.nlm.nih.gov/compound/''N''-acetyl-L-cysteine#section=Chemical-and-Physical-Properties|archive-date=16 August 2016}}</ref>

Acetylcysteine dissolves readily in water, forming a colorless solution. The pH of a 1% acetylcysteine solution in water typically ranges between 2.0 and 2.8.<ref>{{cite web |title=USP Monographs: Acetylcysteine |url=http://ftp.uspbpep.com/v29240/usp29nf24s0_m750.html#usp29nf24s0_m750}}</ref> Solutions with higher concentrations of acetylcysteine have lower pH. Aqueous solutions of acetylcysteine are compatible with 0.9% sodium chloride solution; compatibility with 5% and 10% glucose solutions is also good.<ref name="pmid33638319"/>

As for photochemical stability, acetylcysteine in dry powder form is relatively stable and does not degrade quickly when exposed to light, but in aqueous solution, acetylcysteine can degrade when exposed to sunlight. In addition, acetylcysteine in aqueous solution can undergo hydrolysis, leading to the breakdown of the amide bond in the molecule. Still, aqueous solutions of acetylcysteine are generally stable when stored properly: the solutions should be kept in tightly sealed containers and stored at controlled room temperature to prolong the stability.<ref name="pmid21164069">{{cite journal|doi=10.2146/ajhp100214 |title=Stability of extemporaneously prepared acetylcysteine 1% and 10% solutions for treatment of meconium ileus |date=2011 |journal=American Journal of Health-System Pharmacy |volume=68 |pages=69–72 |pmid=21164069 | vauthors = Fohl AL, Johnson CE, Cober MP |issue=1 }}</ref><ref name="pmid33638319"/>

Acetylcysteine has been reported to have a pH of 2.2 when administered through inhalation.<ref name="Tomkiewicz_1997">{{cite book | vauthors = Tomkiewicz RP, King M, Rubin BK | chapter = Mucoactive Agents: Old and New | title = The Pediatric Lung | pages = 155–179 | date = 1997 | doi = 10.1007/978-3-0348-8960-5_7 | publisher = Birkhäuser Basel | publication-place = Basel | isbn = 978-3-0348-9845-4 | chapter-url = http://link.springer.com/10.1007/978-3-0348-8960-5_7 | access-date = 12 June 2025 | quote = Evidence for the efficacy of acetylcysteine by the aerosol route is less clear and there are reports that inhaled acetylcysteine (PH 2.2) can produce bronchospasm secondary to airway inflammation. }}</ref>

==Society and culture==
[[File:Acetylcysteine Life Extension.jpg|thumb|200px|Acetylcysteine capsules sold by the supplement company [[Biomedical Research & Longevity Society|Life Extension]]]]
[[File:Fluimucil NAC pills in China.jpg|thumb|200px|Over-the-counter (OTC) Acetylcysteine pills in [[China]], with [[brand name]] Fluimucil]]
Acetylcysteine was first studied as a drug in 1963. [[Amazon (company)|Amazon]] removed acetylcysteine for sale in the US in 2021, due to claims by the [[Food and Drug Administration]] (FDA) of it being classified as a drug rather than a supplement.<ref name="Long-2021b">{{cite news |vauthors=Long J |date=6 May 2021 |title=Amazon confirms plans on removing NAC supplements |url=https://www.naturalproductsinsider.com/regulatory/amazon-confirms-plans-removing-nac-supplements |access-date=21 September 2023 |archive-date=16 May 2021 |archive-url=https://web.archive.org/web/20210516105959/https://www.naturalproductsinsider.com/regulatory/amazon-confirms-plans-removing-nac-supplements |url-status=live }}</ref><ref name="Long-2021a">{{cite news | vauthors = Long J | date = 22 April 2021 | work = Natural Products Inside | url = https://www.naturalproductsinsider.com/regulatory/amazon-reportedly-removes-nac-containing-dietary-supplements | title = Amazon reportedly removes NAC-containing dietary supplements | access-date = 16 May 2021 | archive-date = 16 May 2021 | archive-url = https://web.archive.org/web/20210516121310/https://www.naturalproductsinsider.com/regulatory/amazon-reportedly-removes-nac-containing-dietary-supplements | url-status = live }}</ref><ref name="benjaminmcevoy.com">{{cite news |title=Warning Letter benjaminmcevoy.com MARCS-CMS 607149 — May 14, 2020 |url=https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/benjaminmcevoycom-607149-05142020 |publisher=U.S. Food and Drug Administration | date=15 May 2020 |access-date=3 May 2022 |archive-date=3 May 2022 |archive-url=https://web.archive.org/web/20220503215137/https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/benjaminmcevoycom-607149-05142020 |url-status=live }}</ref><ref name="FDA Sends Warning Letters to Seven Companies Illegally Selling Hangover Products">{{cite news |title=FDA Sends Warning Letters to Seven Companies Illegally Selling Hangover Products |url=https://www.fda.gov/food/hfp-constituent-updates/fda-sends-warning-letters-seven-companies-illegally-selling-hangover-products | date=29 July 2020 |access-date=3 May 2022 |archive-date=3 May 2022 |archive-url=https://web.archive.org/web/20220503215141/https://www.fda.gov/food/cfsan-constituent-updates/fda-sends-warning-letters-seven-companies-illegally-selling-hangover-products |url-status=live }}</ref> In April 2022, the FDA released draft guidance on its policy regarding products labeled as dietary supplements that contain ''N''-acetyl-<small>L</small>-cysteine.<ref name="FDA Releases Draft Guidance on Enforcement Discretion for Certain NAC Products">{{cite news|title=FDA Releases Final Guidance on Enforcement Discretion for Certain NAC Products |url=https://www.fda.gov/food/hfp-constituent-updates/fda-releases-final-guidance-enforcement-discretion-certain-nac-products | date=29 November 2023 |access-date=3 May 2022|archive-date=3 May 2022|archive-url=https://web.archive.org/web/20220503215145/https://www.fda.gov/food/cfsan-constituent-updates/fda-releases-draft-guidance-enforcement-discretion-certain-nac-products|url-status=live }}</ref> Amazon subsequently re-listed NAC products as of August 2022.<ref name="Long-2022">{{cite web | vauthors = Long J |title=Amazon resumes sales of NAC supplements |url=https://www.naturalproductsinsider.com/regulatory/amazon-resumes-sales-nac-supplements |website=Natural Products Insider |access-date=11 January 2023 |date=25 August 2022}}</ref>

==Research==

Acetylcysteine is under preliminary research for its potential to treat [[Pattern hair loss|androgenetic alopecia]] (male baldness), with or without adjacent treatments such as with [[minoxidil]].<ref name="QJM-2021">{{cite journal|title= Efficacy and Tolerability of N-Acetyl-Cysteine for Treatment of The Early-onset Androgenetic Alopecia in Men|journal=[[QJM: An International Journal of Medicine]]|editor=[[Oxford University Press]]|issue=Suppl.1|date=October 2021|volume=114|doi=10.1093/qjmed/hcab093.024|author1=Mahira Hamdy El Sayed|author2=Marwa Yassin Soltan|author3=Ahmed Sadek|author4=Mohamed Abo Shabana Hussein Mohamed |article-number=hcab093.024 }}</ref> Acetylcysteine may have otoprotective properties and could be useful for preventing [[hearing loss]] and [[tinnitus]] in some cases.<ref name="Schlee 2024">{{cite book | vauthors = Schlee W, Langguth B, Ridder DD, Vanneste S, Kleinjung T, Møller AR |title=Textbook of Tinnitus |publisher=Springer |year=2024 |edition=2nd |isbn=978-3-031-35646-9 |page=394, 620}}</ref><ref name="pmid36457967">{{cite journal | vauthors = Chang PH, Liu CW, Hung SH, Kang YN | title = Effect of ''N''-acetyl-cysteine in prevention of noise-induced hearing loss: a systematic review and meta-analysis of randomized controlled trials | journal = Archives of Medical Science | volume = 18 | issue = 6 | pages = 1535–1541 | date = 2022 | pmid = 36457967 | pmc = 9710288 | doi = 10.5114/aoms/109126 }}</ref>

Acetylcysteine may be an [[adjunct therapy]] for the treatment of addiction to cocaine, nicotine, alcohol, and other drugs.<ref name="pmid24442756">{{cite journal | vauthors = McClure EA, Gipson CD, Malcolm RJ, Kalivas PW, Gray KM | title = Potential role of ''N''-acetylcysteine in the management of substance use disorders | journal = CNS Drugs | volume = 28 | issue = 2 | pages = 95–106 | date = February 2014 | pmid = 24442756 | pmc = 4009342 | doi = 10.1007/s40263-014-0142-x }}</ref>

===Psychiatry===
Acetylcysteine has been studied for major psychiatric disorders,<ref name="pmid34509090">{{cite journal | vauthors = Bartoli F, Cavaleri D, Bachi B, Moretti F, Riboldi I, Crocamo C, Carrà G | title = Repurposed drugs as adjunctive treatments for mania and bipolar depression: A meta-review and critical appraisal of meta-analyses of randomized placebo-controlled trials | journal = Journal of Psychiatric Research | volume = 143 | pages = 230–238 | date = November 2021 | pmid = 34509090 | doi = 10.1016/j.jpsychires.2021.09.018 | s2cid = 237485915 }}</ref><ref name="pmid21118657"/><ref name="pmid23369637"/><ref name="pmid24683506">{{cite journal | vauthors = Bavarsad Shahripour R, Harrigan MR, Alexandrov AV | title = ''N''-acetylcysteine (NAC) in neurological disorders: mechanisms of action and therapeutic opportunities | journal = Brain and Behavior | volume = 4 | issue = 2 | pages = 108–122 | date = March 2014 | pmid = 24683506 | pmc = 3967529 | doi = 10.1002/brb3.208 }}</ref> including [[bipolar disorder]],<ref name="pmid34509090" /> [[major depressive disorder]], and [[schizophrenia]].<ref name="pmid21118657">{{cite journal | vauthors = Dean O, Giorlando F, Berk M | title = ''N''-acetylcysteine in psychiatry: current therapeutic evidence and potential mechanisms of action | journal = Journal of Psychiatry & Neuroscience | volume = 36 | issue = 2 | pages = 78–86 | date = March 2011 | pmid = 21118657 | pmc = 3044191 | doi = 10.1503/jpn.100057 }}</ref><ref name="pmid23369637">{{cite journal | vauthors = Berk M, Malhi GS, Gray LJ, Dean OM | title = The promise of ''N''-acetylcysteine in neuropsychiatry | journal = Trends in Pharmacological Sciences | volume = 34 | issue = 3 | pages = 167–177 | date = March 2013 | pmid = 23369637 | doi = 10.1016/j.tips.2013.01.001 }}</ref>

Preliminary research indicates ''N''-acetylcysteine may be useful in treating [[obsessive-compulsive disorder]],<ref name="pmid38385640">{{cite journal | vauthors = Carollo M, Carollo N, Montan G | title = The promise of ''N''-acetylcysteine in the treatment of obsessive-compulsive disorder | journal = CNS Neuroscience & Therapeutics | volume = 30 | issue = 2 | article-number = e14653 | date = February 2024 | pmid = 38385640 | pmc = 10883097 | doi = 10.1111/cns.14653 }}</ref> specific [[drug addiction]]s ([[cocaine]]), drug-induced [[Peripheral neuropathy|neuropathy]], [[trichotillomania]], [[excoriation disorder]], and a certain form of epilepsy ([[progressive myoclonic epilepsy|progressive myoclonic]]).<ref name="pmid21118657" /><ref name="pmid23369637"/><ref name="pmid25957927"/> Other research has tested ''N''-acetylcysteine in [[anxiety disorder]], [[attention deficit hyperactivity disorder]] and [[mild traumatic brain injury]], although further studies are required.<ref name="pmid25957927">{{cite journal | vauthors = Slattery J, Kumar N, Delhey L, Berk M, Dean O, Spielholz C, Frye R | title = Clinical trials of ''N''-acetylcysteine in psychiatry and neurology: A systematic review | journal = Neuroscience and Biobehavioral Reviews | volume = 55 | pages = 294–321 | date = August 2015 | pmid = 25957927 | doi = 10.1016/j.neubiorev.2015.04.015 | title-link = doi | doi-access = free }}</ref><ref name="''N''-acetyl cysteine in the treatment">{{cite journal | vauthors = Oliver G, Dean O, Camfield D, Blair-West S, Ng C, Berk M, Sarris J | title = ''N''-acetyl cysteine in the treatment of obsessive compulsive and related disorders: a systematic review | journal = Clinical Psychopharmacology and Neuroscience | volume = 13 | issue = 1 | pages = 12–24 | date = April 2015 | pmid = 25912534 | pmc = 4423164 | doi = 10.9758/cpn.2015.13.1.12 }}</ref>

====Addiction====
Evidence to date does not support the efficacy for ''N''-acetylcysteine in treating [[addiction]]s to [[gambling addiction|gambling]], [[methamphetamine]], or [[nicotine]].<ref name="pmid25957927" />

====Bipolar disorder====
In [[bipolar disorder]], ''N''-acetylcysteine has been repurposed as an augmentation strategy for depressive episodes in light of the possible role of inflammation in the pathogenesis of [[mood disorders]]. Nonetheless, meta-analytic evidence shows that add-on ''N''-acetylcysteine was more effective than placebo only in reducing depression scales scores (low quality evidence), without positive effects on response and remission outcomes, limiting its possible role in clinical practice to date.<ref name="pmid34509090" /><ref name="pmid33354859">{{cite journal | vauthors = Nery FG, Li W, DelBello MP, Welge JA | title = ''N''-acetylcysteine as an adjunctive treatment for bipolar depression: A systematic review and meta-analysis of randomized controlled trials | journal = Bipolar Disorders | volume = 23 | issue = 7 | pages = 707–714 | date = November 2021 | pmid = 33354859 | doi = 10.1111/bdi.13039 | s2cid = 229692736 }}</ref>

=== COVID-19 ===
Acetylcysteine has been studied as a possible treatment for [[COVID-19]], but has not improved patient outcomes by common measures.<ref>{{cite journal | vauthors = Paraskevas T, Kantanis A, Karalis I, Michailides C, Karamouzos V, Koniari I, Pierrakos C, Velissaris D | title = N-acetylcysteine efficacy in patients hospitalized with COVID-19 pneumonia: a systematic review and meta-analysis | journal = Romanian Journal of Internal Medicine | volume = 61 | issue = 1 | pages = 41–52 | date = March 2023 | pmid = 36627753 | doi = 10.2478/rjim-2023-0001 | doi-access = free | hdl = 2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/372692 | hdl-access = free }}</ref>

== External links ==
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== References ==
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