N-Acetyl Cysteine

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N-Acetyl Cysteine


N-Acetyl Cysteine

NAC (N-acetyl cysteine) is an altered form of the amino acid cysteine, which is commonly found in food and synthesized by the body.

What Are "Star" Ratings?

a7_3star   Reliable and relatively consistent scientific data showing a substantial health benefit.

a7_2star   Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

a7_1star   For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

This supplement has been used in connection with the following health conditions:

Used for Amount Why
400 to 600 mg daily 3 stars   NAC, which appears to work by reducing the thickness of mucus, has been shown to be a safe and effective treatment for chronic bronchitis.

3 stars  Bronchitis

400 to 600 mg daily

A review of 39 clinical trials of NAC (N-acetyl cysteine) found that 400 to 600 mg per day was a safe and effective treatment for chronic bronchitis.1 NAC supplementation was found to reduce the number of aggravations of the illness in almost 50% of people taking the supplement, compared with only 31% of those taking placebo. Smokers have also been found to benefit from taking NAC.2 In addition to helping break up mucus, NAC may reduce the elevated bacterial counts that are often seen in the lungs of smokers with chronic bronchitis.3 In another double-blind study, people with chronic bronchitis who took NAC showed an improved ability to expectorate and a reduction in cough severity.4 These benefits may result from NAC’s capacity to reduce the viscosity (thickness) of sputum.5

Used for Amount Why
Chronic Obstructive Pulmonary Disease
200 mg three times daily 3 stars   N-acetyl cysteine helps break down mucus and supplies antioxidant protection to lung tissue.

3 stars  Chronic Obstructive Pulmonary Disease

200 mg three times daily

NAC (N-acetyl cysteine) helps break down mucus. For that reason, inhaled NAC is used in hospitals to treat bronchitis. NAC may also protect lung tissue through its antioxidant activity.6 Oral NAC, 200 mg taken three times per day, is also effective and improved symptoms in people with bronchitis in double-blind research.7 , 8 However, NAC was ineffective in one study.9 Results may take six months. NAC does not appear to be effective for people with COPD who are taking inhaled steroid medications.10

Used for Amount Why
600 mg three times daily (under medical supervision if taking nitroglycerin) 2 stars   Under a doctor’s supervision, supplementing with NAC may improve the effects of nitroglycerin.

2 stars  Angina

600 mg three times daily (under medical supervision if taking nitroglycerin)

NAC (N-acetyl cysteine) may improve the effects of nitroglycerin in people with angina.11 People with unstable angina who took 600 mg of NAC three times daily in combination with a nitroglycerin transdermal (skin) patch for four months had significantly lower rates of subsequent heart attacks than did people who used either therapy alone or placebo.12

Used for Amount Why
1 gram daily 2 stars   In one study, people with atrophic gastritis given NAC saw increased healing.

2 stars  Gastritis

1 gram daily

Various amino acids have shown promise for people with gastritis. In a double-blind trial, taking 200 mg of cysteine four times daily provided significant benefit for people with bleeding gastritis caused by NSAIDs (such as aspirin).13 Cysteine is a sulfur-containing amino acid that stimulates healing of gastritis. In a preliminary trial, 1–4 grams per day of NAC (N-acetyl cysteine) given to people with atrophic gastritis for four weeks appeared to increase healing.14 Glutamine, another amino acid is a main energy source for cells in the stomach and supplementation may increase blood flow to this region.15 Patients in surgical intensive care units often develop gastrointestinal problems related to a glutamine deficiency.16 When burn victims were supplemented with glutamine, they did not develop stress ulcers, even after several operations.17 Nevertheless, it remains unclear to what extent glutamine supplementation might prevent or help existing gastritis. Preliminary evidence suggests the amino acid arginine may both protect the stomach and increase its blood flow,18 but research has yet to investigate the effects of arginine supplementation in people with gastritis.

Used for Amount Why
Heart Attack
Consult a qualified healthcare practitioner 2 stars   In one study, NAC injections decreased the amount of tissue damage in people who had suffered a heart attack.

2 stars  Heart Attack

Consult a qualified healthcare practitioner

In one study, intravenous injections of NAC (N-acetyl cysteine) decreased the amount of tissue damage in people who had suffered a heart attack.[REF] Whether oral NAC would have the same effect is unknown.

Used for Amount Why
HIV and AIDS Support
800 mg daily 2 stars   Supplementing with NAC may slow the decline in immune function.

2 stars  HIV and AIDS Support

800 mg daily

The amino acid NAC (N-acetyl cysteine) has been shown to inhibit the replication of HIV in test tube studies.19 In a double-blind trial, supplementing with 800 mg per day of NAC slowed the rate of decline in immune function in people with HIV infection. NAC also promotes the synthesis of glutathione, a naturally-occurring antioxidant that is believed to be protective in people with HIV infection and AIDS.20

Used for Amount Why
600 mg three times per day 1 star   In a case report, a woman with kidney disease due to SLE (lupus nephritis) may have had an improvement in her kidney function due to treatment with N-acetylcysteine (NAC).

1 star  Lupus

600 mg three times per day

In a case report, a woman with kidney disease due to SLE (lupus nephritis) had an improvement in her kidney function and was able to taper off of her steroid medicine after starting treatment with N-acetylcysteine (NAC) in the amount of 600 mg 3 times per day. She continued NAC, and after a total of 13 months her disease was considered inactive.21

How It Works

How to Use It

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.

Where to Find It

Cysteine , the amino acid from which NAC is derived, is found in most high-protein foods. NAC is not found in the diet.

Possible Deficiencies

Deficiencies of NAC have not been defined and may not exist. Deficiencies of the related amino acidcysteine have been reported in HIV-infected patients.22


Interactions with Supplements, Foods, & Other Compounds

At the time of writing, there were no well-known interactions with this supplement.

Interactions with Medicines

Certain medicines interact with this supplement.

May Be Beneficial: Some medicines may increase the need for this supplement.
Avoid: Some medicines interact with this supplement, so they should not be taken together.
Check: Some interactions between this supplement and certain medicines require more explanation. Click the link to see details.

Note: The following list only includes the generic or class name of a medicine. To find a specific brand name, use the Medicines Index.

May Be Beneficial: Acetaminophen
May Be Beneficial: Acetaminophen with Codeine
May Be Beneficial: Bicalutamide
May Be Beneficial: Busulfan
May Be Beneficial: Capecitabine
May Be Beneficial: Carboplatin
May Be Beneficial: Carmustine
May Be Beneficial: Chlorambucil
May Be Beneficial: Cisplatin
May Be Beneficial: Cladribine
May Be Beneficial: Clozapine
May Be Beneficial: Cortisone
May Be Beneficial: Cyclophosphamide
May Be Beneficial: Cytarabine
May Be Beneficial: Dexamethasone
May Be Beneficial: Docetaxel
May Be Beneficial: Erlotinib
May Be Beneficial: Etoposide
May Be Beneficial: Floxuridine
May Be Beneficial: Fludarabine
May Be Beneficial: Fluorouracil
May Be Beneficial: Flurbiprofen
May Be Beneficial: Gentamicin
May Be Beneficial: Hydrocodone-Acetaminophen
May Be Beneficial: Ifosfamide
May Be Beneficial: Ifosfamide
May Be Beneficial: Irinotecan
May Be Beneficial: Isoniazid
May Be Beneficial: Isoniazid-Rifampin
May Be Beneficial: Isoniazid-Rifamp-Pyrazinamide
May Be Beneficial: Isosorbide Dinitrate
May Be Beneficial: Isosorbide Mononitrate
May Be Beneficial: Lomustine
May Be Beneficial: Melphalan
May Be Beneficial: Mercaptopurine
May Be Beneficial: Methotrexate
May Be Beneficial: Methylprednisolone
May Be Beneficial: Paclitaxel
May Be Beneficial: Polifeprosan 20 with Carmustine
May Be Beneficial: Prednisolone
May Be Beneficial: Prednisone
May Be Beneficial: Streptozocin
May Be Beneficial: Thioguanine
May Be Beneficial: Thiotepa
May Be Beneficial: Uracil Mustard
May Be Beneficial: Vinblastine
May Be Beneficial: Vincristine
Avoid: Metoclopramide
Check: AZT
Check: Doxorubicin
Check: Mechlorethamine
Check: Nitroglycerin

Side Effects

Side Effects

One study reported that 19% of people taking NAC orally experienced nausea, vomiting, headache, dry mouth, dizziness, or abdominal pain.23 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.24 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.25 Therefore, supplemental zinc and copper should be added when supplementing with NAC for extended periods.


1. Stey C, Steurer J, Bachmann S, et al. The effect of oral N-acetylcysteine in chronic bronchitis: a quantitative systematic review. Eur Respir J 2000;16:253–62 [review].

2. Boman G, Backer U, Larsson S, et al. Oral acetylcysteine reduces exacerbation rate in chronic bronchitis: report of a trial organized by the Swedish Society for Pulmonary Diseases. Eur J Respir Dis 1983;64:405–15.

3. Riise GC, Larsson S, Larsson P, et al. The intrabronchial microbial flora in chronic bronchitis patients: a target for N-acetylcysteine therapy? Eur Respir J 1994;7:94–101.

4. Jackson IM, Barnes J, Cooksey P. Efficacy and tolerability of oral acetylcysteine (Fabrol) in chronic bronchitis: a double-blind placebo controlled study. J Int Med Res 1984;12:198–206.

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

6. Van Schayck CP, Dekhuijzen PN, Gorgels WJ, et al. Are anti-oxidant and anti-inflammatory treatments effective in different subgroups of COPD? A hypothesis. Respir Med 1998;92:1259–64.

7. 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.

8. Multicenter Study Group. Long-term oral acetylcysteine in chronic bronchitis. A double-blind controlled study. Eur J Respir Dis 1980;61:111:93–108.

9. Schermer T, Chavannes N, Dekhuijzen R, et al. Fluticasone and N-acetylcysteine in primary care patients with COPD or chronic bronchitis. Respir Med 2009;103:542–51.

10. Decramer M, Rutten-van Molken M, Dekhuijzen PN, et al. Effects of N-acetylcysteine on outcomes in chronic obstructive pulmonary disease (Bronchitis Randomized on NAC Cost-Utility Study, BRONCUS): a randomised placebo-controlled trial. Lancet2005;365:1552–60.

11. Marchetti G, Lodola E, Licciardello L, Colombo A. Use of N-acetylcysteine in the management of coronary artery diseases. Cardiologia 1999;44:633–7.

12. 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 1997;29:941–7.

13. Salim AS. Sulfhydryl-containing agents in the treatment of gastric bleeding induced by non-steroidal anti-inflammatory drugs. Can J Surg 1993;36(1):53–8.

14. Farinati F, Cardin R, Della Libera G, et al. Effects of N-acetyl-L-cysteine in patients with chronic atrophic gastritis and nonulcer dyspepsia: a phase III pilot study. Curr Ther Res 1997;58:724–33.

15. Houdijk AP, Van Leeuwen PA, Boermeester MA, et al. Glutamine-enriched enteral diet increases splanchnic blood flow in the rat. Am J Physiol 1994;267(6 Pt 1):G1035–40.

16. Wilmore DW, Smith RJ, O’Dwyer ST, et al. The gut: a central organ after surgical stress. Surgery 1988;104:917–23.

17. Yan R, Sun Y, Sun R. Early enteral feeding and supplement of glutamine prevent occurrence of stress ulcer following severe thermal injury. Chung Hua Cheng Hsing Shao Shang Wai Ko Tsa Chih 1995;11(3):189–92.

18. Brzozowski T, Konturek SJ, Sliwowski Z, et al. Role of L-arginine, a substrate for nitric oxide-synthase, in gastroprotection and ulcer healing. J Gastroenterol 1997;32(4):442–52.

19. Roederer M, Staal FJ, Raju PA, et al. Cytokine-stimulated human immunodeficiency virus replication is inhibited by N-acetyl-L-cysteine. Proc Natl Acad Sci 1990;87:4884–8.

20. Herzenberg LA, De Rosa SC, Dubs JG, et al. Glutathione deficiency is associated with impaired survival in HIV disease. Proc Natl Acad Sci 1997;94:1967–72.

21. Tewthanom K, Janwitayanujit S, Totemchockcyakarn K, et al. The effect of high dose of N-acetylcysteine in lupus nephritis: a case report and literature review. J Clin Pharm Ther 2010;35:483–5.

22. 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.

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

24. 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.

25. 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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