N-Acetyl Cysteine

Also indexed as: Acetylcysteine, NAC

What does it do? N-acetyl cysteine (NAC) is an altered form of the amino acid cysteine, 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, 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 The second 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.

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):

Rating Health Concerns
3Stars Acetaminophen poisoning
Bronchitis (chronic)
Chronic obstructive pulmonary disease (COPD)
2Stars Angina pectoris
Gastritis
Heart Attack (IV immediately following a myocardial infarction)
HIV support
Unverricht-Lundborg Disease
1Star Pseudoporphyria
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star An herb is primarily supported by traditional use, or the herb or supplement has little scientific support and/or minimal health benefit.

Who is likely to be deficient? Deficiencies of NAC have not been defined and may not exist. Deficiencies of the related amino acid, cysteine, have been reported in HIV-infected patients.11

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.12 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.13 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.14 Therefore, supplemental zinc and copper should be added when supplementing with NAC for extended periods.

Are there any drug interactions? Certain medications may interact with N-Acetyl Cysteine. Refer to the drug interactions safety check for a list of those medications.

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. 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.

12. Tattersall AB, Bridgman KM, Huitson A. Acetylcysteine (Fabrol) in chronic bronchitis—a study in general practice. J Int Med Res 1983;11:279–84.

13. 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.

14. 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.