N-Acetyl Cysteine

background

N-acetyl cysteine (NAC) is made from the amino acid L-cysteine. It is a source of sulfhydryl (-SH) groups and, thus, may act as a strong antioxidant.
Because it has the ability to thin mucus, NAC has been used traditionally as a decongestant. It has also been used to reduce poisoning associated with compounds such as acetaminophen and heavy metals.
NAC has been used clinically for approximately 40 years and has shown benefit for treating bronchiolitis and chronic bronchitis. Recent study has investigated its role as an antioxidant with the potential to treat HIV infection, cancer, and heart conditions. There is a lack of evidence of benefit in using NAC to prevent kidney impairment or to treat hepatitis, cystic fibrosis, or erythropoietic protoporphyria (a disorder caused by a defect in making heme).
NAC is generally well tolerated. The most frequent side effects are diarrhea, nausea, and vomiting. NAC is also well known for its unpleasant taste.

Related Terms

Acetadote®, acetiscisteína, acetylcistein natrium, acetylcysteine, CAS 616-91-1, cysteine, dacistein, Fabrol(, Fluimucil(, Flumacil®, Hidonac®, L-cysteine, L-cysteine HCl, Lysomucil®, Mucomyst®, N-acetil cysteine, N-acetyl-B-cysteine, N-acetylcysteine.

evidence table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
 
Acetaminophen toxicity (Grade: A)
Strong scientific evidence supports the use of N-acetyl cysteine (NAC) as an antidote to acetaminophen overdose.
Bronchiolitis (sulfur mustard-induced) (Grade: B)
NAC is commonly used for lung infections and sputum (phlegm and mucus) clearance. In human study, NAC reduced symptoms in patients with sulfur mustard-induced bronchiolitis (swelling in the small air passages of the lungs). Additional study is needed before a conclusion can be made.
Chronic bronchitis (Grade: B)
NAC has been used to treat chronic bronchitis since the 1960s. Evidence from some human studies suggests that NAC may benefit patients with chronic bronchitis. Other studies show a lack of benefit. Further study is required before firm conclusions can be made.
Acute respiratory distress syndrome (ARDS) (Grade: C)
Limited human study has investigated the effect of NAC on acute respiratory distress syndrome (ARDS). NAC may improve ventilation support. Additional research is needed.
Acute respiratory infections (Grade: C)
Preliminary studies suggest that NAC may benefit patients with acute respiratory infections. Because the patients studied were also taking other medications, additional studies testing the effect of NAC alone are needed.
Addiction (gambling) (Grade: C)
In preliminary study, NAC appeared to decrease measures of pathological gambling. Further well-designed research is required before a conclusion can be made.
Adrenoleukodystrophy (a type of fat breakdown disorder) (Grade: C)
Preliminary evidence of benefit of NAC for adrenoleukodystrophy has been found. Further well-designed research is required before a conclusion can be made.
Alzheimer's disease (Grade: C)
Limited human study investigating the effect of NAC on Alzheimer's disease has shown improvement in one assessment of memory and a lack of effect on others. Additional well-designed trials are needed before a conclusion can be made.
Amyotrophic lateral sclerosis (Grade: C)
Limited study showed a lack of benefit of NAC in patients with amyotrophic lateral sclerosis. Further study is needed.
Angina (chest pain from clogged heart arteries) (Grade: C)
Results of studies on the effect of NAC on angina are mixed. Further well-designed clinical trials are needed before a conclusion may be made.
Asthma (Grade: C)
Preliminary study suggests that NAC may improve lung function in asthma patients. Additional study is required.
Cancer (Grade: C)
Although not well-studied in humans, NAC has been shown to have a possible anti-cancer effect. However, preliminary human study reported a lack of benefit of NAC in increasing survival time of cancer patients. Additional research is needed before firm conclusions can be made.
Chemotherapy adverse effects (Grade: C)
Limited study suggests that NAC may decrease side effects of chemotherapy. However, results from different studies conflict. Further well-designed clinical trials are required.
Chronic lung conditions (infantile) (Grade: C)
There is a lack of sufficient evidence to make a conclusion on the use of NAC to treat chronic lung disease in infants. Preliminary human study suggests a lack of benefit of NAC in this group. Further study is required in this area.
Chronic obstructive pulmonary disease (COPD) (Grade: C)
There is a lack of sufficient evidence to make a conclusion regarding the use of NAC in the treatment of chronic obstructive lung disease. Well-designed clinical trials are needed.
Cocaine withdrawal (Grade: C)
Limited study showed that NAC may decrease the desire to use cocaine in cocaine-dependent patients. Well-designed study is needed before firm conclusions may be made.
Depression (Grade: C)
In preliminary study, patients with bipolar disorder had decreased symptoms of depression when NAC was used together with standard treatment. Further well-designed study is required before a conclusion can be made.
Diminished appetite (high-altitude anorexia) (Grade: C)
Preliminary study suggests that NAC may be ineffective in treatment of high-altitude appetite reduction. Further study is required before a conclusion can be made.
Dry eye syndrome (Grade: C)
Preliminary research suggests that eye drops containing NAC may help treat dry eye syndrome. Further research is required.
Exercise performance enhancement (Grade: C)
Antioxidants may decrease exercise-associated muscle pain and fatigue and, thus, may increase exercise endurance. In limited study, NAC increased exercise endurance. Further well-designed research is required before a conclusion may be made.
Female infertility (Grade: C)
Preliminary research showed that NAC lacked benefit as an adjunct to a fertility drug in women with unexplained infertility. Further research is required before a conclusion may be made.
Heart protection during coronary artery bypass grafting (CABG) (Grade: C)
NAC has been investigated for its potential to protect against heart damage following coronary artery bypass grafting (CABG). The clinical effects of NAC were unclear. Further research is required before firm conclusions may be made.
Helicobacter pylori infection (Grade: C)
Although not well-studied in humans, NAC treatment was found to reduce the degree of
HIV/AIDS (Grade: C)
The results of limited study on the effect of NAC on HIV/AIDS are unclear. Additional research is needed.
Hyperhomocysteinemia (high blood levels of homocysteine) (Grade: C)
High blood levels of homocysteine may increase the risk of heart disease. Preliminary human study showed that NAC decreased homocysteine levels in patients with high blood levels of homocysteine, in patients with kidney disease, and in healthy people. It is unclear if NAC decreases the risk of heart disease. Well-designed studies are required before conclusions may be made in this area.
Hyperlipidemia (Lp(a)) (Grade: C)
Results of different studies investigating the effect of NAC on reducing levels of certain blood lipids conflict. Further evidence is required before a conclusion may be made.
Influenza prevention (Grade: C)
Limited human study suggests that regular NAC use may help prevent influenza. Additional research is needed.
Malaria (Grade: C)
In limited human research, NAC failed to help patients with malaria. Further research is needed before a conclusion may be made.
Male infertility (Grade: C)
In limited research, NAC improved sperm concentration in infertile males. Further research is required.
Miscarriage prevention (Grade: C)
In women with a history of miscarriages, NAC plus folate decreased the rate of miscarriage compared with folate treatment alone. Additional study is needed.
Multiple organ failure (Grade: C)
Results of preliminary study suggest NAC may not prevent multiple organ failure. Further well-designed studies are required before a conclusion may be made.
Myocardial ischemia (decreased blood flow to the heart) (Grade: C)
Results of preliminary research suggest that NAC may help patients who have had a heart attack. Well-designed human studies are needed before conclusions can be made.
Nosebleed (Grade: C)
In preliminary research, NAC reduced the frequency and severity of daytime nosebleed. Further research is needed.
Organ transplantation (liver) (Grade: C)
Preliminary study showed a lack of benefit of NAC in liver transplantation. Further research is required before a conclusion may be made.
Osteoporosis/post-menopausal bone loss (Grade: C)
Results of study of NAC for osteoporosis/post-menopausal bone loss are unclear. Further well-designed research is required before a conclusion may be made.
Pancreatitis (inflammation of the pancreas) (Grade: C)
In limited study, NAC lacked benefit for pancreatitis prevention. Further information is required in this field.
Peripheral artery disease (Grade: C)
There is limited human study on the use of NAC for peripheral artery disease. Further well-designed research is required before a conclusion may be made.
Plaque formation (Grade: C)
In preliminary study, an oral rinse containing NAC reduced plaque formation. Further research is required.
Polycystic ovarian syndrome (Grade: C)
Limited evidence suggests NAC may increase ovulation and pregnancy and improve insulin levels in women with polycystic ovarian syndrome (PCOS). Results are mixed, however, and further research is needed.
Postoperative recovery (coronary) (Grade: C)
NAC has been investigated for its potential in aiding recovery from heart surgery. Further research in this field is warranted.
Pregnancy support (Grade: C)
NAC has been studied for its possible benefit in reducing preterm labor in pregnant women with a previous history of preterm labor. Further research is needed in this field before a conclusion may be made.
Schizophrenia (Grade: C)
In preliminary research, NAC has been investigated as a treatment for schizophrenia. Further well-designed research is required before a conclusion may be made.
Sepsis (Grade: C)
There is limited human study on the use of NAC for sepsis treatment. Further evidence is needed.
Sjögren's syndrome (Grade: C)
There is a lack of sufficient evidence to make a conclusion for or against the use of NAC in the treatment of Sjögren's syndrome. Well-designed clinical trials are required.
Trauma (acoustic) (Grade: C)
Limited study showed a lack of effect of NAC on hearing in people exposed to loud noise. Further research is required in this field.
Ulcerative colitis (a type of inflammatory bowel disease) (Grade: C)
NAC has been investigated as a treatment for ulcerative colitis. Further well-designed research is required.
Cystic fibrosis (Grade: D)
There is fairly strong evidence suggesting that NAC is not useful in the treatment of cystic fibrosis. Well-designed studies are needed to make a firm conclusion.
Erythropoietic protoporphyria (disorder involving abnormal heme synthesis) (Grade: D)
Available evidence suggests NAC is ineffective for erythropoietic protoporphyria. Further evidence is required before a firm conclusion may be made.
Hepatitis (Grade: D)
There is fairly strong evidence that NAC does not increase a hepatitis patient's response to interferon therapy. Additional research is needed.
Kidney dysfunction (impairment) (Grade: D)
Until further information is available, there is a lack of sufficient evidence for or against the use of NAC for the prevention of kidney damage. More research is needed.