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Other Names:

Acetyl Cysteine, Acétyl Cystéine, Acetylcysteine, Acétylcystéine, Chlorhydrate de Cystéine, Cysteine, Cystéine, Cysteine Hydrochloride, Cystine, Hydrochlorure de Cystéine, L-Cysteine, L-Cystéine, L-Cysteine HCl, L-Cystéine HCl, NAC, N-Acetil Cis...
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N-ACETYL CYSTEINE Overview Information

N-acetyl cysteine comes from the amino acid L-cysteine. Amino acids are the building blocks of proteins. N-acetyl cysteine has many uses as medicine.

N-acetyl cysteine is used to counteract acetaminophen (Tylenol) and carbon monoxide poisoning. It is also used for chest pain (unstable angina), bile duct blockage in infants, amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease), Alzheimer’s disease, allergic reactions to the anti-seizure drug phenytoin (Dilantin), and an eye infection called keratoconjunctivitis. It is also used for reducing levels of a type of cholesterol called lipoprotein (a), homocysteine levels (a possible risk factor for heart disease) and the risk of heart attack and stroke in patients with serious kidney disease.

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 H1N1 (swine) flu; and for detoxifying heavy metals such as mercury, lead, and cadmium.

N-acetyl cysteine is also used for preventing alcoholic liver damage; for protecting against environmental pollutants including carbon monoxide, chloroform, urethanes and certain herbicides; for reducing toxicity of ifosfamide and doxorubicin, drugs that are used for cancer treatment; as a hangover remedy; for preventing kidney damage due to certain X-ray dyes; and for human immunodeficiency virus (HIV).

Healthcare providers give N-acetyl cysteine intravenously (by IV) for 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.

N-acetyl cysteine is sometimes inhaled (breathed into the lungs) or delivered through a tube in the throat to treat certain lung disorders such as pneumonia, bronchitis, emphysema, cystic fibrosis, and others.

How does it work?

N-acetyl cysteine treats acetaminophen (Tylenol) poisoning by binding the poisonous forms of acetaminophen that are formed in the liver. It is also an antioxidant, so it may play a role in preventing cancer.

N-ACETYL CYSTEINE Uses & Effectiveness What is this?

Effective for:

  • Helping to prevent crusting in people with a tube in their windpipe (people who have undergone a tracheostomy).
  • Acetaminophen (Tylenol) poisoning. N-acetyl cysteine is effective in reducing the death rate and preventing the permanent harm caused by acetaminophen poisoning. For this use, N-acetyl cysteine given by mouth is as effective as N-acetyl cysteine given intravenously (by IV).
  • Reducing mucus and helping with breathing in various lung conditions.
  • Cystic fibrosis.

Possibly Effective for:

  • Preventing problems such as heart attack and stroke in people with serious kidney disease. The risk reduction can be as much as 40%. However, N-acetyl cysteine doesn’t reduce the overall risk of death or death from heart disease in these people.
  • Chest pain (angina).
  • Preventing complications of chronic bronchitis.
  • Preventing complications of lung disease (chronic obstructive pulmonary disease, COPD).
  • Preventing side effects of ifosfamide (Ifex), which is used for certain types of cancer.
  • Preventing kidney problems with dyes used during some X-ray exams.
  • Reducing homocysteine levels, a possible risk factor for heart disease.
  • Reducing symptoms of the flu.
  • Reducing symptoms of hair pulling.
  • Treating some types of epilepsy seizures.
  • Treating a lung disease called fibrosing alveolitis.

Possibly Ineffective for:

  • Preventing side effects of doxorubicin (used for treating certain types of cancer).
  • Treating amyotrophic lateral sclerosis (ALS, Lou Gehrig’s disease).

Likely Ineffective for:

  • Preventing new tumors in people with head and neck cancer, or lung cancer.
  • Treating Alzheimer’s disease.
  • Improving how the body responds to nitroglycerin (Nitrostat).
  • Treating organ failure.

Insufficient Evidence for:

  • Colon cancer. Taking N-acetyl cysteine may reduce the likelihood of colon and rectal cancer in patients with a history of adenomatous colon polyps.
  • Heart attack. Early evidence shows that N-acetyl cysteine given by IV along with nitroglycerin and another drug called streptokinase may reduce heart damage in people having a heart attack.
  • Carbon monoxide poisoning.
  • Allergic reactions to phenytoin (Dilantin).
  • Ear infections.
  • Hay fever.
  • Removing heavy metals such as mercury, lead, and cadmium from the body.
  • Chronic fatigue syndrome (CFS).
  • Preventing alcoholic liver damage.
  • Protecting against environmental pollutants.
  • Other conditions.
More evidence is needed to rate the effectiveness of N-acetyl cysteine for these uses.

N-ACETYL CYSTEINE Side Effects & Safety

N-acetyl cysteine is LIKELY SAFE for most adults, when used as a prescription medication. It can cause nausea, vomiting, and diarrhea or constipation. Rarely, it can cause rashes, fever, headache, drowsiness, low blood pressure, and liver problems.

When inhaled (breathed into the lungs), it can also cause swelling in the mouth, runny nose, drowsiness, clamminess, and chest tightness.

N-acetyl cysteine has an unpleasant odor that may make it hard to take.

Special Precautions & Warnings:

Pregnancy or breast-feeding: N-acetyl cysteine is POSSIBLY SAFE when taken by mouth, delivered through a hole in the windpipe, or breathed in. N-acetyl cysteine crosses the placenta, but there is no evidence so far linking it with harm to the unborn child or mother. However, N-acetyl cysteine should only be used in pregnant women when clearly needed, such as in cases of acetaminophen toxicity.

Allergy: Don’t use N-acetyl cysteine if you are allergic to acetyl cysteine.

Asthma: There is a concern that N-acetyl cysteine might cause bronchospasm in people with asthma if inhaled or taken by mouth or through a tube in the windpipe. If you take N-acetyl cysteine and have asthma, you should be monitored by your healthcare provider.

N-ACETYL CYSTEINE Interactions What is this?

Major Interaction Do not take this combination

  • Nitroglycerin interacts with N-ACETYL CYSTEINE

    Nitroglycerin can dilate blood vessels and increase blood flow. Taking N-acetyl cysteine seems to increase the effects of nitroglycerin. This could cause increased chance of side effects including headache, dizziness, and lightheadedness.

Moderate Interaction Be cautious with this combination

  • Activated charcoal interacts with N-ACETYL CYSTEINE

    Activated charcoal is sometimes used to prevent poisoning in people who take too much acetaminophen and other medications. Activated charcoal can bind up these medications in the stomach and prevent them from being absorbed by the body. Taking N-acetyl cysteine at the same time as activated charcoal might decrease how well it works for preventing poisoning.


The following doses have been studied in scientific research:


  • For acetaminophen (Tylenol) overdose: at the beginning of treatment, a first high dose of 140 mg/kg of a 5% solution of N-acetyl cysteine is given. The commercially available 10% and 20% solutions may be diluted with water, carbonated, or non-carbonated beverages, and given through a straw to lessen the unpleasant odor of N-acetyl cysteine. Seventeen additional doses of 70 mg/kg as a 5% solution are given every 4 hours, for a total dose of 1330 mg/kg over 72 hours.
  • For chest pain that is not relieved by rest (unstable angina): 600 mg of N-acetyl cysteine three times daily with a nitroglycerin patch.
  • For preventing sudden worsening of chronic bronchitis: doses of 200 mg twice daily, 200 mg three times daily, 300 mg slow-release twice daily, and 600 mg controlled-release twice daily have been used.
  • For treating chronic obstructive pulmonary disease (COPD): 600 mg of N-acetyl cysteine once daily, in addition to standard care, has been used for up to 6 months.
  • For treating a lung condition called fibrosing alveolitis that makes breathing difficult: 600 mg of N-acetyl cysteine 3 times daily.
  • For preventing damage to the bladder due to treatment with a cancer drug called ifosfamide: 1 to 2 grams of N-acetyl cysteine every 6 hours.
  • For reducing levels of homocysteine in the blood: 1.2 grams of N-acetyl cysteine daily.
  • For myoclonus epilepsy: 4-6 grams daily.
  • For reducing flu symptoms: 600 mg twice daily.
  • For reducing the risk of heart attacks and strokes in patients with end-stage kidney disease: 600 mg twice daily.
  • For skin wounds due to hemodialysis treatment: 200 mg four times daily or 600 mg twice daily.
  • For preventing kidney damage associated with the use of iopromide (Ultravist-300) for diagnostic tests: 400 to 600 mg of N-acetyl cysteine twice daily on the day before and on the day of iopromide administration, with IV saline (0.45%) 1 mL/kg body weight per hour for 12 hours before and 12 hours after iopromide administration.
  • For trichotillomania (hair-pulling): N-acetyl cysteine 1200 mg to 2400 mg daily has been used.
  • Healthcare providers give N-acetyl cysteine intravenously (by IV) for acetaminophen poisoning.

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Conditions of Use and Important Information: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is provided by Natural Medicines Comprehensive Database Consumer Version. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version. © Therapeutic Research Faculty 2009.

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