Acetylcysteine

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N-acetylcysteine
)

Acetylcysteine
Clinical data
Pronunciation/əˌsiːtəlˈsɪstiːn/ and similar (/əˌsɛtəl-, ˌæsɪtəl-, -tiːn/)
Trade namesACC 200, Acetadote, Fluimucil, Mucomyst, others
Other namesN-acetylcysteine; N-acetyl-L-cysteine; NALC; NAC
AHFS/Drugs.comMonograph
License data
Pregnancy
category
  • AU: B2
inhalation
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability10% (Oral)[6]
Protein binding50 to 83%[7]
MetabolismLiver[7]
Elimination half-life5.6 hours[5]
ExcretionKidney (30%),[7] faecal (3%)
Identifiers
  • (2R)-2-acetamido-3-sulfanylpropanoic acid[8]
JSmol)
Specific rotation+5° (c = 3% in water)[9]
Melting point109 to 110 °C (228 to 230 °F) [9]
  • C/C(=N/[C@@H](CS)C(=O)O)/O
  • InChI=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 checkY
  • Key:PWKSKIMOESPYIA-BYPYZUCNSA-N checkY
  (verify)

Acetylcysteine, also known as N-acetylcysteine (NAC), is a

lactobezoar in infants. It can be taken intravenously, by mouth, or inhaled as a mist.[7] Some people use it as a dietary supplement.[10][11]

Common side effects include nausea and vomiting when taken by mouth.

mucolytic by decreasing the thickness of mucus.[12]

Acetylcysteine was initially patented in 1960 and came into medical use in 1968.

generic medication.[18]

The sulfur-containing amino acids cysteine and methionine are more easily oxidized than the other amino acids.[19][20]

Uses

Medical uses

Paracetamol overdose

Main article: Paracetamol poisoning

Intravenous and oral formulations of acetylcysteine are available for the treatment of

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 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.[22] 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.[22] Research suggests that the rate of liver toxicity is approximately 3% when acetylcysteine is administered within 10 hours of overdose.[21]

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,[23] its foul taste and odour, and a higher incidence of adverse effects when taken by mouth, particularly nausea and vomiting. Prior pharmacokinetic studies of acetylcysteine did not consider acetylation as a reason for the low bioavailability of acetylcysteine.[24] Oral acetylcysteine is identical in bioavailability to cysteine precursors.[24] 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), a decrease in blood pressure, rash, angioedema, and sometimes also nausea and vomiting.[25] 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.[26][27][28][29]

Lungs

Inhaled acetylcysteine has been used for

mucolytic ("mucus-dissolving") 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.[30] A 2013 Cochrane review in cystic fibrosis found no evidence of benefit.[31]

Acetylcysteine is used in the treatment of obstructive lung disease as an adjuvant treatment.[32][33][34]

Other uses

Acetylcysteine has been used to complex palladium, to help it dissolve in water. This helps to remove palladium from drugs or precursors synthesized by palladium-catalyzed coupling reactions.[35] N-acetylcysteine can be used to protect the liver.[36]

Microbiological use

Acetylcysteine can be used in Petroff's method of liquefaction and decontamination of

influenza A viruses.[38]

Acetylcysteine has

bactericidal properties and breaks down bacterial biofilms of clinically relevant pathogens including Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis, Enterobacter cloacae, Staphylococcus epidermidis, and Klebsiella pneumoniae.[39]

Side effects

"SNOAC" redirects here. For the gene, see
snoaC
.

The most commonly reported adverse effects for IV formulations of acetylcysteine are rash,

itchiness.[22]

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.[40]

Adverse effects for oral formulations of acetylcysteine have been reported to include nausea, vomiting, rash, and fever.[40]

Large doses in a mouse model showed that acetylcysteine could potentially cause damage to the

hypoxia). The authors also found that SNOAC induced a hypoxia-like response in the expression of several important genes 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.

hypoxia.[42]

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.[43]

Pharmacology

Pharmacodynamics

Acetylcysteine serves as a

L-cysteine, a precursor to the biologic antioxidant glutathione. Hence administration of acetylcysteine replenishes glutathione stores.[44]

L-cysteine also serves as a precursor to

BDNF), and the regulation of neuronal cell death through B‐cell lymphoma 2 expression (BLC-2).[52]

Pharmacokinetics

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.

Chemistry

Acetylcysteine is the N-

free radicals
.

N-acetyl-L-cysteine is soluble in water and alcohol, and practically insoluble in chloroform and ether.[53]

It is a white to white with light yellow cast powder, and has a

pKa of 9.5 at 30 °C.[9]

Society and culture

Acetylcysteine was first studied as a drug in 1963. Amazon removed acetylcysteine for sale in the US in 2021, due to claims by the FDA of it being classified as a drug rather than a supplement.[54][55][56][57] In April 2022, the FDA released draft guidance on FDA's policy regarding products labeled as dietary supplements that contain N-acetyl-L-cysteine.[58] Amazon subsequently re-listed NAC products as of August 2022.[59]

Research

While many antioxidants have been researched to treat a large number of diseases by reducing the negative effect of oxidative stress, acetylcysteine is one of the few that has yielded promising results, and is currently already approved for the treatment of paracetamol overdose.[60]

Kidney and bladder

Evidence for the benefit of acetylcysteine to prevent

radiocontrast induced kidney disease is mixed.[73]

Acetylcysteine has been used for

cystitis, although mesna is generally preferred due to the ability of acetylcysteine to diminish the effectiveness of cyclophosphamide.[74]

Psychiatry

Acetylcysteine has been studied for major psychiatric disorders,[75][52][48][62] including bipolar disorder,[75] major depressive disorder, and schizophrenia.[52][48]

Tentative evidence exists for N-acetylcysteine also in the treatment of

mild traumatic brain injury although confirmatory studies are required.[77][78][79][80] Tentative evidence also supports use in cannabis use disorder.[81]

It is also being studied for use as a treatment of body-focused repetitive behavior.[82][83]

Addiction

Evidence to date does not support the efficacy for N-acetylcysteine in treating

excitatory amino acid transporter 2 (EAAT2), a.k.a. glutamate transporter 1 (GLT1), in individuals with addiction.[69] While NAC has been demonstrated to modulate glutamate neurotransmission in adult humans who are addicted to cocaine, NAC does not appear to modulate glutamate neurotransmission in healthy adult humans.[69] NAC has been hypothesized to exert beneficial effects through its modulation of glutamate and dopamine neurotransmission as well as its antioxidant properties.[48]

Bipolar disorder

In

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.[75][84]

COVID-19

Acetylcysteine is being considered as a possible treatment for COVID-19.[85][86][87]

A combination of guanfacine and N-acetylcysteine has been found to lift the "brain fog" of eight patients with long COVID, according to researchers.[88]

A combination of glycine and N-acetylcysteine is suspected to have potential to safely replenish depleted glutathione levels in COVID-19 patients.[89]

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