N-Acetyl Cysteine




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.

People take N-acetyl cysteine by mouth to counteract acetaminophen (Tylenol) and carbon monoxide poisoning. It is also used for chest pain (unstable angina), bipolar disorder, genetic conditions known as lysosomal storage disorders, 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), an eye infection called keratoconjunctivitis, and influenza symptoms. It is also used for reducing levels of a type of blood fat called lipoprotein (a), homocysteine levels (a possible risk factor for heart disease), and the risk of heart attack and stroke in people with serious kidney disease.

N-acetyl cysteine is also taken by mouth for hepatitis, kidney disease, hearing loss, ulcerative colitis, polycystic ovary syndrome (PCOS), low blood pressure, lupus, certain conditions that occur after menopause, muscle damage due to exercise, schizophrenia, recovery after surgery, swelling of the pancreas (pancreatitis), cocaine dependence, altitude sickness, infection due to Helicobacter pylori bacteria, and for decreasing the risk for heart rhythm problems after surgery. It may also be used for genetic conditions known as adrenoleukodystrophy (ALD), erythropoietic protoporphyria (EPP), and hereditary hemorrhagic telangiectasia (HHT).

Some people use N-acetyl cysteine orally for long-term bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis, hay fever, human immunodeficiency virus (HIV), a lung condition called fibrosing alveolitis, autism, head and neck cancer, colorectal 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. It may be used for preventing sports injury complications, miscarriages, preterm labor, and liver damage due to alcohol use. Some people use N-acetyl cysteine to improve fertility and immunity to flu and H1N1 (swine) flu. It is also used for detoxifying heavy metals such as mercury, lead, and cadmium.

N-acetyl cysteine is also taken by mouth for protecting against environmental pollutants including carbon monoxide, chloroform, urethanes and certain herbicides; reducing toxicity of drugs used for cancer treatment; treating hangover symptoms; preventing kidney damage due to certain X-ray dyes; and treating compulsive hair pulling (trichotillomania).

N-acetyl cysteine is applied to the skin to treat a genetic condition known as lamellar ichthyosis. It is also applied inside the mouth to reduce dental plaque. Also, it is applied to the eye to improve dry eyes.

Healthcare providers give N-acetyl cysteine intravenously (by IV) for acetaminophen (Tylenol) overdose, acrylonitrile poisoning, amyotrophic lateral sclerosis (ALS, Lou Gehrig's disease), kidney failure in the presence of liver disease (hepatorenal syndrome), pancreas swelling (pancreatitis), 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. Intravenously, N-acetyl cysteine may also be used to improve recovery after surgery, decrease heart rhythm problems after surgery, treat a genetic condition known as adrenoleukodystrophy (ALD), improve exercise performance, treat acute respiratory distress syndrome (ARDS), improve lung function in patients with sepsis, and prevent kidney damage due to certain X-ray dyes. It is also used for pancreatitis, liver transplants, malaria, and cardiac bypass graft (CABG) surgery. It is also given by IV to reduce nitrate tolerance.

N-acetyl cysteine is sometimes used rectally for conditions known as meconium ileus and meconium ileus equivalent.

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 asthma, pneumonia, chronic obstructive pulmonary disease (COPD), bronchitis, emphysema, cystic fibrosis, and others. It is also used to help prepare people for diagnostic lung tests and to help care for people with a tube in their windpipe.

How it works

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.


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).

Collapse of part or all of a lung (atelectasis)

N-acetyl cysteine helps treat collapsed lungs caused by mucus blockage.

Diagnostic lung tests

N-acetyl cysteine is helpful when used to prepare people for diagnostic lung tests.

Care of people with a tube in their windpipe (people who have undergone a tracheostomy)

N-acetyl cysteine helps prevent crusting in people with a tube in their windpipe.


Likely safe

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.



Pregnancy or breast-feeding: N-acetyl cysteine isPOSSIBLY SAFEwhen taken by mouth, delivered through a hole in the windpipe, or inhaled by women who are pregnant. N-acetyl cysteine crosses theplacenta, but there is no evidence that it harms the unborn child ormother. But N-acetyl cysteine should only be used in pregnant women when medically needed.

There is not enough reliable information about the safety of taking N-acetyl cysteine if you are breast-feeding. Stay on the safe side and avoid use.

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.

Bleeding disorder. N-acetyl cysteine might slow blood clotting. There is concern that N-acetyl cysteine might increase the risk of bruising and bleeding in people with bleeding disorders.

Surgery. N-acetyl cysteine might slow blood clotting. This might increase the risk of bleeding during and after surgery. Stop taking N-acetyl cysteine at least 2 weeks before a scheduled surgery.


Always consult with your doctor.

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.

Activated charcoal

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.

Chloroquine (Aralen)

Chloroquine (Aralen) is a drug used to treat malaria. It kills malaria by causing a chemical called heme to build up inside of cells. N-acetyl cysteine might prevent the build-up of heme inside of cells. This might reduce the effects of chloroquine.

The information provided on this page is for reference purposes and is not meant to be used as a medical advice, diagnosis or treatment. Always consult with a medical professional.