Also indexed as: Acetylcysteine, NAC
What does it do?
N-acetyl cysteine (NAC) is an altered form of the amino
acidcysteine, which is commonly found in food and
synthesized by the body.
NAC helps break down mucus. Double-blind research has found that NAC supplements improved
symptoms and prevented recurrences in people with chronic
bronchitis.1 2 3 NAC may also protect lung tissue through
its antioxidant activity.4
NAC helps the body synthesize glutathione, an
important antioxidant. In animals, the antioxidant activity of NAC protects the liver from the
adverse effects of exposure to several toxic chemicals. NAC also protects the body from acetaminophen toxicity and is used at very high levels in
hospitals for patients with acetaminophen poisoning. It has also been shown to be effective at
treating liver failure from causes other than acetaminophen poisoning (e.g., hepatitis, and other drug toxicity)5 and at
preventing kidney damage caused by injections of iopromide, a contrast medium used in people
scheduled to undergo computerized tomography (CT) imaging.6
Supplementation with NAC has been shown to reduce the proliferation of certain cells lining
the colon and may reduce the risk of colon cancer in
people with recurrent polyps in the colon.7
There have been several case reports of oral NAC producing dramatic improvements in
Unverricht-Lundborg disease, an inherited degenerative disorder involving seizures and
progressive disability.8 9 One study used 3 grams of NAC per day.
Oral supplementation with NAC has been used successfully in two cases to treat a rare
syndrome that complicates kidney dialysis.10 This condition, known as
pseudoporphyria, has no other known treatment. Controlled clinical trials are needed to
confirm these preliminary observations.
People undergoing a certain cardiac procedure (coronary angiography) are at risk of
developing kidney damage from the injected dye that is used to visualize the coronary
arteries. In a double-blind study, oral administration of NAC reduced by 86% the incidence of
kidney damage in people undergoing this procedure.11 The amount of NAC used in that
study was 400 mg twice a day, on the day before and the day of the procedure.12
Other studies have shown that NAC is protective only when a low dose of dye is used.
Where is it found?
Cysteine, the amino
acid from which NAC is derived, is found in most high-protein foods. NAC is not found in
the diet.
N-acetyl cysteine has been
used in connection with the following conditions (refer to the
individual health concern for complete information):
Who is likely to be deficient?
Deficiencies of NAC have not been defined and may not exist. Deficiencies of the related amino acidcysteine have
been reported in HIV-infected
patients.13
How much is usually taken?
Healthy people do not need to supplement NAC. Optimal levels of supplementation remain
unknown, though much of the research uses 250–1,500 mg per day.
Are there any side effects or interactions?
One study reported that 19% of people taking NAC orally experienced nausea, vomiting,
headache, dry mouth, dizziness, or abdominal pain.14 These symptoms have not been
consistently reported by other researchers, however.
Although a great deal of research has shown that NAC has antioxidant activity, one small study found that daily amounts
of 1.2 grams or more could lead to increased oxidative stress.15 Extremely
large amounts of cysteine, the amino acid from which NAC is derived, may be toxic to nerve
cells in rats.
NAC may increase urinary zinc excretion.16 Therefore, supplemental zinc and copper should be added when
supplementing with NAC for extended periods.
Are there any drug
interactions?
Certain medicines may interact with N-Acetyl Cysteine. Refer to drug interactions for a list of those
medicines.
References
1. Boman G, Bäcker U, Larsson S, et al. Oral acetylcysteine reduces
exacerbation rate in chronic bronchitis: a report of a trial organized by the Swedish Society
for Pulmonary Diseases. Eur J Respir Dis 1983;64:405–15.
2. Multicenter Study Group. Long-term oral acetylcysteine in chronic
bronchitis. A double-blind controlled study. Eur J Respir Dis
1980;61:111:93–108.
3. Grandjean EM, Berthet P, Ruffmann R, Leuenberger P. Efficacy of oral
long-term N-Acetylcysteine in chronic bronchopulmonary disease: A meta-analysis of
published double-blind, placebo-controlled clinical trials. Clin Ther
2000;22:209–21.
4. Van Schayck CP, Dekhuijzen PNR, Gorgels WJMJ, et al. Are anti-oxidant
and anti-inflammatory treatments effective in different subgroups of COPD? A hypothesis.
Respir Med 1998;92:1259–64.
5. Ben-Ari Z, Vaknin H, Tur-Kaspa R. N-acetylcysteine in acute hepatic
failure (non-paracetamol-induced). Hepatogastroenterology 2000;47:786–9.
6. Tepel M, van der Giet M, Schwarzfeld C, et al. Prevention of
radiographic-contrast-agent-induced reductions in renal function by acetylcysteine. N Engl
J Med 2000;343:180–4.
7. 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 1999;147:109–14.
8. Hurd RW, Wilder BJ, Helveston WR, Utham BM. Treatment of four siblings
with progressive myoclonus epilepsy of the Unverricht-Lundborg type with
N-acetylcysteine. Neurology 1996;47:1264–8.
9. Selwa LM. N-Acetylcysteine therapy for Unverricht-Lundborg
disease. Neurology 1999;52:426–7.
10. Vadoud-Seyedi J, de Dobbeleer G, Simonart T. Treatment of
haemodialysis-associated pseudoporphyria with N-acetylcysteine: report of two cases. Br J
Dermatol 2000;142:580–1.
11. Shyu KG, Cheng JJ, Kuan P. Acetylcysteine protects against acute
renal damage in patients with abnormal renal function undergoing a coronary procedure. J
Am Coll Cardiol 2002;40:1383–8.
12. Shyu KG, Cheng JJ, Kuan P. Acetylcysteine protects against acute
renal damage in patients with abnormal renal function undergoing a coronary procedure. J
Am Coll Cardiol 2002;40:1383–8.
13. de Quay B, Malinverni R, Lauterburg BH. Glutathione depletion in
HIV-infected patients: role of cysteine deficiency and effect of oral N-acetylcysteine.
AIDS 1992;6:815–9.
14. Tattersall AB, Bridgman KM, Huitson A. Acetylcysteine (Fabrol) in
chronic bronchitis—a study in general practice. J Int Med Res
1983;11:279–84.
15. Kleinveld HA, Demacker PNM, Stalenhoef AFH. Failure of
N-acetylcysteine to reduce low-density lipoprotein oxidizability in healthy subjects. Eur
J Clin Pharmacol 1992;43:639–42.
16. Brumas V, Hacht B, Filella M, Berthon G. Can N-acetyl-L-cysteine
affect zinc metabolism when used as a paracetamol antidote? Agents Actions
1992;36:278–88.
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The information presented in Healthnotes is for informational
purposes only. It is based on scientific studies (human, animal, or in vitro),
clinical experience, or traditional usage as cited in each article. The results reported may
not necessarily occur in all individuals. For many of the conditions discussed, treatment with
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before making any changes in prescribed medications. Information expires March 2005.
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