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N-acetylcysteine (NAC)


Acetylcysteine, also known as N-acetylcysteine or N-acetyl-L-cysteine (abbreviated NAC). It is a sulphur-containing amino acid and it is the precursor of the amino acids L-cysteine and glutathione.

N-acetyl-L-cysteine is made from the amino acid cysteine joined to an acetyl group. This nutrient is a strong antioxidant. It donates the amino acid cysteine to help form the antioxidant glutathione, a powerful natural antioxidant normally found in the body.

NAC, a more stable form of L-Cysteine, is one of the best sources to obtain higher glutathione levels, and to promote better anti-toxin potential to assist in a healthier immune system.

NAC has very similar results as L-Cysteine due to the Glutathione levels provided, but is more stable because of its acetyl properties (CH3CO) and is better water soluble, as well as said to be more bio-available than L-Cysteine.

There are three different forms of Acetylcysteine: N-acetyl-L-cysteine (NAC): Is the active form that is naturally produced in the human body. As a pharmaceutical drug and nutritional supplement it is produced synthetically, because it can not be obtained from any natural source. The compound is a white crystalline powder which melts in the range of 104 to 110C and has a very slight odor.

N-acetyl-D-cysteine (D-NAC): Is an N-acetyl amino acid. It is the enantiomer of the common N-Acetyl-L-cysteine. N-Acetyl-D-cysteine is a detoxified version of D-cysteine. N-acetyl-d-cysteine cannot be enzymatically converted into intracellular glutathione (GSH) and is therefore (far) less active then N-acetyl-L-cysteine and primarily used for science purposes.


NAC has been used in conventional medicine for more than 30 years, primarily as a mucolytic (mucous-thinner) inhaled to manage conditions such as cystic fibrosis, in which mucous is abnormally thick and tenacious. While there is little in the scientific literature to support its use as an inhalant, NAC administered in this form remains highly popular among experienced pulmonary specialists.

NAC given intravenously or orally, on the other hand, saves lives every year as a treatment for acute poisoning with acetaminophen-containing pain-relieving drugs. NAC quickly restores protective levels of glutathione, averting catastrophe.

Beyond this particular application, NAC has remained a relatively obscure and poorly understood compound until quite recently scientists all over the world are now beginning to understand just how vital glutathione metabolism really is, and how many disease states involve glutathione deficiency. According to Stanford University's Dr. Kondala R. Atkuri, "NAC has been used successfully to treat glutathione deficiency in a wide range of infections, genetic defects and metabolic disorders, including HIV infection and COPD. Over two-thirds of 46 placebo-controlled clinical trials with orally administered NAC have indicated beneficial effects of NAC measured either as trial endpoints or as general measures of improvement in quality of life and well-being of the patients."

NAC stucture Photo: (R)-N-Acetyl-L-Cysteine Structural Formulae
NAC powder Photo: N-acetyl-L-cysteine powder


N-acetyl-L-cysteine or its products were on market and consumed to a significant degree before 15 May 1997 and are therefore, according the EU Novel Food Regulation, allowed to be used as or in food and as a food supplement.

There are many different N-acetyl-L-cysteine sold over the counter in tablet and capsule form and as a topical solution. It is also available as a prescription in aerosol sprays for inhalation and liquid solutions for intravenous infusion.

The aerosol sprays are used for mucolytic therapy or ingested for nephroprotective effect (to protect the kidneys) and to treat certain lung disorders such as pneumonia, bronchitis, emphysema, cystic fibrosis, and others.

The liquid solutions are used for treatment of paracetamol/acetaminophen overdose, acrylonitrile poisoning, amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease), kidney failure in the presence of liver disease (hepatorenal syndrome), chest pain in combination with nitroglycerin, heart attack in combination with nitroglycerin and streptokinase, and for helping to prevent multi-organ failure leading to death.

Lately, cosmetic compositions containing N-acetyl-L-cysteine have been introduced, such as creams, lotions and permanent wave lotions.

N-acetyl-L-cysteine for use in cosmetics, is as such mentioned as an antioxidant in EU Decision 96/335/EG from EU Cosmetic Directive 76/768/EEG and/or 2006/257/EG.

Medicinal actions

N-Acetyl-L-Cysteine is a great amino acid that can boost the levels of glutathione in the body, which provides for a healthier immune system. Glutathione, as a non-essential nutrient, but yet powerful anti-oxidant that helps prevent oxidative cell damage and reduces the damaging effects of environmental toxins, is responsible for maintaining healthy antioxidant levels in the body. Its purpose is activating certain enzymes, and it plays an important role in carbohydrate metabolism as well.

Some people use N-acetyl cysteine for chronic bronchitis, chronic obstructive pulmonary disease (COPD), hay fever, a lung condition called fibrosing alveolitis, head and neck cancer, and lung cancer. It is also used for treating some forms of epilepsy; ear infections; complications of kidney dialysis; chronic fatigue syndrome (CFS); an autoimmune disorder called Sjogren's syndrome; preventing sports injury complications; radiation treatment; increasing immunity to flu; and for detoxifying heavy metals such as mercury, lead, and cadmium.

Other uses include sulfate repletion in conditions, such as autism, where cysteine and related sulfur amino acids may be depleted.

NAC replenishes levels of the intracellular antioxidant glutathione (GSH), which is often deficient with advancing age and in chronic illness. It also regulates expression of scores of genes in the pathways that link oxidative stress to inflammation.

Administration has historically been as a mucolytic [mucus dissolving] agent in a variety of respiratory illnesses; however, it appears to also have beneficial effects in conditions characterized by decreased glutathione or oxidative stress, such as HIV infection, cancer, heart disease, and cigarette smoking.

The most common applications of N-acetyl-L-cysteine are: So far the European Food Safety Authority (EFSA) did not approve any submitted Health claims and therefore none are authorized in the EU.

Industrial application

There are no industrial applications found for N-acetyl-L-cysteine other than medicinal.


The LD50 of NAC is 7888 mg/kg in mice and 5050 mg/kg in rats following oral doses. In animal fertility studies, no adverse affects were reported at doses up to 250 mg/kg and no teratogenic effects were observed at doses as high as 2000 mg/kg.

The typical oral dose for NAC as a mucolytic agent and for most other clinical indications is 600-1500 mg NAC daily in three divided doses.

For the therapeutic treatment of amongst others; heart disease, chest pain that is not relieved by rest (unstable angina) and myoclonus epilepsy, the dosage usually is in the range of 2 to 4 grams and sometimes even 6 grams per day.

For acetaminophen poisoning, NAC is usually administered orally with a loading dose of 140 mg/kg and 17 subsequent doses of 70 mg/kg every four hours. In acetaminophen poisoning, it is important to begin administering NAC within 8-10 hours of overdose to ensure effectiveness.

The University of Michigan Health System notes the following daily doses were used in clinical trials evaluating NAC for various conditions: An active dosage of N-acetyl-L-cysteine in cosmetics has not been established and can therefore not be given. Though, it might be plausible that the noticeable effects should increase along with the increase of dosage.


NAC is generally safe and well tolerated even at high doses, but there are some warnings when using N-acetyl-L-cysteine:

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