N-Acetylcysteine

N-Acetylcysteine

N-Acetylcysteine

Common Names

  • Acetylcysteine
  • NAC

For Patients & Caregivers

N-acetylcysteine is an effective drug for acetaminophen overdose and to break up mucus. It has not been proven to be an effective treatment for cancer.

N-acetylcysteine (NAC) is a compound that is found naturally in the body. It is converted to a chemical called glutathione, which plays a role in the detoxification of foreign substances in the body. It is used as an antidote for acetaminophen overdose. NAC itself is an antioxidant that is thought to neutralize free radicals that cause damage to DNA. Animals fed with NAC have less cellular damage and fewer lung, colon, and bladder tumors, compared with those fed a normal diet. In addition, NAC interferes with tumor invasion, metastasis, and blood vessel growth in lab experiments. However, few of these effects have been shown to occur in humans. An animal study shows NAC can speed up the growth of lung cancer cells due to its antioxidant activity.

NAC can dissolve and loosen mucus in patients with respiratory disorders such as chronic bronchitis and chronic obstructive pulmonary disease (COPD), but study results are mixed. Animal studies also show that it might protect against tissue damage from drugs such as doxorubicin, ifosfamide, and cyclophosphamide. These effects are currently being studied in humans.

NAC regulates glutamate levels in the brain. It has been studied for several psychiatric disorders in humans with limited success.

  • To treat lung conditions such as bronchitis and COPD
    Clinical trials evaluating NAC for prevention of exacerbations of chronic bronchitis due to its mucus-digesting effect are mixed.
  • To treat cystic fibrosis
    A meta-analysis found a small, but not very significant effect of inhaled N-acetylcysteine on lung function in patients with cystic fibrosis (9)
  • To prevent and treat cancer
    Most clinical trials do not support the use of N-acetylcysteine for treating cancer. A few clinical trials suggest that this supplement can prevent certain pre-cancerous damage, but there is no proof that it can prevent cancer.
  • To treat drug-induced liver toxicity
    N-acetylcysteine is an effective treatment for acetaminophen poisoning (2), which can be life-threatening. If hepatic toxicity is suspected, seek immediate medical attention for proper treatment. One study also observed that NAC has a protective effect against liver toxicity from antituberculosis drugs.
  • To treat cirrhosis
    Although N-acetylcysteine is known to be a precursor for glutathione, an important detoxification enzyme in the liver, there is no proof from clinical trials that this supplement can treat cirrhosis.
  • To treat HIV and AIDS
    A few clinical trials suggest that N-acetylcysteine can raise cysteine and glutathione levels in HIV+ patients, but whether this supplement improves survival or immunity to disease is not known.
  • To treat Lou Gehrig’s Disease (amyotrophic lateral sclerosis)
    This use has only been tested in one clinical trial, in which it was found that N-acetylcysteine had no effect on progression of disease or survival in patients with Lou Gehrig’s disease.
  • To treat psychiatric disorders
    Several small scale studies suggest NAC may help to control substances and gambling addictions. It may also help to reduce symptoms of trichotillomania (hair pulling) .
  • NAC is used as an antidote for liver toxicity caused by acetaminophen poisoning, which can be life-threatening. If acetaminophen overdose is suspected, seek immediate medical attention for proper treatment.
  • You are taking nitroglycerin:  N-acetylcysteine (NAC) can increase hypotension, headache, and worsen temporal artery dilation.
  • Stomach upset
  • Diarrhea
  • Nausea
  • Vomiting
  • Fatigue
  • Irritation of the conjunctiva of the eyes
  • Skin rash
  • Less commonly reported side effects include low blood pressure, anaphylactic shock, asthma attacks, and headache.
  • It is controversial whether antioxidants like N-acetylcysteine can lessen or negate the effects of chemotherapy and radiation therapy. Because these therapies work by creating free radicals that kill cancer cells, high levels of antioxidants may neutralize these effects and protect cancer cells from these therapies. So what protects healthy cells may protect cancer cells as well. Patients who are interested in taking antioxidants during therapy should consult with their doctor.
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For Healthcare Professionals

N-Acetylcysteine

N-acetylcysteine (NAC) is an antioxidant that is used as a prescription drug and as a dietary supplement. As a drug, it is given parenterally or orally to treat acetaminophen overdose. The inhalant and oral solution forms have a mucolytic effect to relieve obstructions in bronchial diseases and in tracheotomy procedures. The oral capsule is marketed as a dietary supplement for its liver protective function and is popular among patients with AIDS and cancer.

Clinical studies show NAC can treat drug-induced hepatotoxicity (1) (2), prevent and treat conditions of oxidative stress and reduced GSH levels caused by diseases such as HIV/AIDS (3) and cancer (4), and alleviate toxicity from chemo- and radiotherapy (4).

Results for treatment of chronic lung disease with NAC are mixed. NAC reduces the number of acute exacerbations in patients with chronic bronchopulmonary disease (5)and significantly improves lung function and endurance in COPD patients after exercise (6), but these effects were not observed in other trials (7) (8). NAC has no significant benefits in patients with cystic fibrosis (9) or with Lou Gehrig’s disease (10).

NAC has glutamate modulating effects (11) and has been tested as a treatment for psychiatric disorders (12) including addictions (13) and substance abuse (11). It also reduced symptoms of trichotillomania (14) .

Studies in smokers (15) and patients with a history of adenomatous colonic polyps (16) show NAC inhibits cancer biomarker development, although it did not inhibit the formation of secondary head and neck or lung tumors (17). Preliminary studies suggest oral NAC may help reduce chemotherapy-induced neuropathy (18). However, NAC accelerated lung cancer growth in an animal model (36).

Gastrointestinal side effects from the consumption of NAC have been reported (19). Due to its antioxidant activity, it may interfere with the actions of some chemotherapy drugs.

Food is not a significant source of N-acetylcysteine.

  • Prevention of drug-induced hepatotoxicity
  • Cirrhosis
  • Bronchitis
  • Chronic obstructive pulmonary disorders
  • Cystic fibrosis
  • HIV and AIDS
  • Lou Gehrig’s disease
  • Cancer prevention
  • Prevention of chemo- and radiotherapy side effects

NAC is a precursor to glutathione (GSH). It is used as both an antidote for acetaminophen-induced hepatotoxicity and as a mucolytic agent for respiratory diseases. NAC reduces disulphide bonds to sulfhydryl bonds to reduce mucus formation (20). Its hepatoprotective action may occur by cytokine-mediated mechanisms as well as GSH replenishment (21). In animal studies, NAC exhibits chemopreventive effects against lung (22), hepatocellular (23), esophageal (24), and immune system (25) cancers.

An in vitro study shows NAC may improve the benefit of ifosfamide by decreasing the risk of nephrotoxicity without interfering with the agent’s antitumor effect (26). Another study finds that NAC alters doxorubicin-induced NF-κB activity via concentration-dependent anti- and pro-oxidant mechanisms (27). This biphasic effect is also time-dependent (28). In androgen-independent human prostate cancer PC-3 cells, NAC has an antiproliferative effect by upregulating Cyr61 protein expression (28).

NAC amide can increase bioavailability and reduce oxidative stress, but it does not decrease doxorubicin-induced cell death in H9c2 cardiomyocytes (29). In an animal study, NAC increased lung cancer cell proliferation due to its antioxidant activity by reducing reactive oxygen species (ROS), DNA damage and p53 expression (36).

NAC crosses the blood-brain barrier and increases the brain GSH levels. NAC acts as a glutamine modulator (11) and plays a role in treating psychiatry disorders (12).

Common (Oral): Gastrointestinal disturbance, diarrhea, nausea, vomiting, fatigue, conjunctival irritation, skin rash (26) (28)
Reported: Hypotension, anaphylaxis, asthma attacks, headache (29)

Nitroglycerin: Severe headache due to added vasodilation effect (34).
Antidepressants: May increase the effects of imipramine and escitalopram (35).


  1. Baniasadi S, Eftekhari P, Tabarsi P, et al. Protective effect of N-acetylcysteine on antituberculosis drug-induced hepatotoxicity. Eur J Gastroenterol Hepatol. Oct 2010;22(10):1235-1238.

  2. Al-Tonbary Y, Al-Haggar M, El-Ashry R, et al. Vitamin e and N-acetylcysteine as antioxidant adjuvant therapy in children with acute lymphoblastic leukemia. Advances in hematology. 2009;2009:689639.

  3. Schermer T, Chavannes N, Dekhuijzen R, et al. Fluticasone and N-acetylcysteine in primary care patients with COPD or chronic bronchitis. Respir Med. Apr 2009;103(4):542-551.

  4. Duijvestijn YC, Brand PL. Systematic review of N-acetylcysteine in cystic fibrosis. Acta Paediatr. Jan 1999;88(1):38-41.

  5. Louwerse ES, Weverling GJ, Bossuyt PM, et al. Randomized, double-blind, controlled trial of acetylcysteine in amyotrophic lateral sclerosis. Arch Neurol. Jun 1995;52(6):559-564.

  6. Schmaal L, Veltman DJ, Nederveen A, et al. N-acetylcysteine normalizes glutamate levels in cocaine-dependent patients: a randomized crossover magnetic resonance spectroscopy study. Neuropsychopharmacology. Aug 2012;37(9):2143-2152.

  7. Dean O, Giorlando F, Berk M. N-acetylcysteine in psychiatry: current therapeutic evidence and potential mechanisms of action. J Psychiatry Neurosci. Mar 2011;36(2):78-86.

  8. Grant JE, Kim SW, Odlaug BL. N-acetyl cysteine, a glutamate-modulating agent, in the treatment of pathological gambling: a pilot study. Biol Psychiatry. Sep 15 2007;62(6):652-657.

  9. Van Schooten FJ, Besaratinia A, De Flora S, et al. Effects of oral administration of N-acetyl-L-cysteine: a multi-biomarker study in smokers. Cancer Epidemiol Biomarkers Prev. Feb 2002;11(2):167-175.

  10. Estensen RD, Levy M, Klopp SJ, et al. N-acetylcysteine suppression of the proliferative index in the colon of patients with previous adenomatous colonic polyps. Cancer Lett. Dec 1 1999;147(1-2):109-114.

  11. Mullins ME, Schmidt RU, Jr., Jang TB. What is the rate of adverse events with intravenous versus oral N-acetylcysteine in pediatric patients? Ann Emerg Med. Nov 2004;44(5):547-548; author reply 548-549.

  12. Sadowska AM, Verbraecken J, Darquennes K, et al. Role of N-acetylcysteine in the management of COPD. International journal of chronic obstructive pulmonary disease. 2006;1(4):425-434.

  13. Masubuchi Y, Nakayama J, Sadakata Y. Protective effects of exogenous glutathione and related thiol compounds against drug-induced liver injury. Biol Pharm Bull. Mar 2011;34(3):366-370.

  14. Balansky R, Ganchev G, Iltcheva M, et al. Prevention of cigarette smoke-induced lung tumors in mice by budesonide, phenethyl isothiocyanate, and N-acetylcysteine. Int J Cancer. Mar 1 2010;126(5):1047-1054.

  15. Chen N, Hanly L, Rieder M, et al. The effect of N-acetylcysteine on the antitumor activity of ifosfamide. Can J Physiol Pharmacol. May 2011;89(5):335-343.

  16. Lee YJ, Lee DM, Lee CH, et al. Suppression of human prostate cancer PC-3 cell growth by N-acetylcysteine involves over-expression of Cyr61. Toxicology in vitro : an international journal published in association with BIBRA. Feb 2011;25(1):199-205.

  17. Holdiness MR. Clinical pharmacokinetics of N-acetylcysteine. Clin Pharmacokinet. Feb 1991;20(2):123-134.

  18. Olsson B, Johansson M, Gabrielsson J, et al. Pharmacokinetics and bioavailability of reduced and oxidized N-acetylcysteine. Eur J Clin Pharmacol. 1988;34(1):77-82.

  19. Pendyala L, Schwartz G, Bolanowska-Higdon W, et al. Phase I/pharmacodynamic study of N-acetylcysteine/oltipraz in smokers: early termination due to excessive toxicity. Cancer Epidemiol Biomarkers Prev. Mar 2001;10(3):269-272.

  20. Herr SM. Herb-Drug Interaction Handbook, 2nd ed. Nassau, NY: Church Street Books; 2002.

  21. Ardissino D, Merlini PA, Savonitto S, et al. Effect of transdermal nitroglycerin or N-acetylcysteine, or both, in the long-term treatment of unstable angina pectoris. J Am Coll Cardiol. Apr 1997;29(5):941-947.

  22. Costa-Campos L, Herrmann AP, Pilz LK, et al. Interactive effects of N-acetylcysteine and antidepressants. Prog Neuropsychopharmacol B ol Psychiatry. Feb 16 2013;44C:125-130.

  23. Sayin V, Ibrahim M, Larsson E, et al. Antioxidants Accelerate Lung Cancer Progression in Mice. Sci Transl Med. Jan 2014; 6:(221):ra15.

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