Cysteine

Uses:

N-acetyl cysteine (NAC) may be used in preventing or treating the following conditions:

Acetaminophen poisoning

Intravenous (IV) NAC is often given to people who have taken an overdose of acetaminophen (Tylenol), to prevent or reduce liver and kidney damage. Acetaminophen poisoning can also occur at lower doses if someone drinks alcohol or takes certain medications that may damage the liver on a regular basis.

Angina

In clinical studies of people with ongoing chest pain, NAC, in combination with nitroglycerin (a drug that opens up blood vessels and improves blood flow), has been more effective than either NAC or nitroglycerin alone in reducing subsequent chest pain, heart attack, and the risk of death. However, the combination can also cause a severe headache. You should not try to treat chest pain on your own; always see a doctor.

Chronic bronchitis and Chronic Obstructive Pulmonary Disease (COPD)

A review of clinical studies found that NAC may help improve symptoms associated with chronic bronchitis, leading to fewer flare ups. However, one large study failed to find any reduction in flare ups among people with chronic bronchitis. In another study of people with moderate to severe COPD, taking NAC decreased the number of flare ups about 40% when used with other therapies.

Influenza

In one six-month study, people who took 600 mg of NAC twice daily had fewer flu symptoms than those who took placebo.

Acute Respiratory Distress Syndrome (ARDS)

Acute respiratory distress syndrome (ARDS) develops after an injury or trauma to the lungs and is life-threatening. Although not all studies agree, some research (laboratory and human) suggests that intravenous NAC may boost levels of glutathione and help prevent and/or treat lung damage caused by ARDS. However, results of other studies have been conflicting. In one study, giving NAC or Procysteine (a synthetic cysteine) to people with ARDS helped reduce the severity of their condition. But it did not reduce the number of overall deaths compared to placebo.

HIV/AIDS

Some researchers have investigated whether cysteine can help improve levels of glutathione in people with HIV or AIDS. In one well-designed clinical study of people with HIV, those who took daily supplements including the amino acid glutamine (40 grams per day), vitamin C (800 mg), vitamin E (500 IU), beta-carotene (27,000 IU), selenium (280 mcg), and N-acetylcysteine (2400 mg) gained more weight after 12 weeks than those who took placebo. Similarly, in a smaller-scale clinical study where HIV positive patients took NAC, the supplement did increase glutathione levels while a placebo did not. Other clinical studies, however, have shown negative results using NAC for those with HIV. More research is needed to see whether NAC has any benefit for people with HIV.

Other Uses

NAC has also been proposed for the following conditions, although evidence is limited:

• Reducing symptoms associated with Sjögren’s syndrome (an autoimmune disorder characterized by dry mouth and dry eyes)
• Reducing symptoms of asthma, cystic fibrosis, and emphysema
• Preventing colon cancer
• Preventing cataracts and macular degeneration
• Helping increase HDL “good” cholesterol
• Helping increase fertility when taken along with fertility drugs in people with polycystic ovary disease
• Helping improve outcome in children with advanced cerebral adrenoleukodystrophy, a type of leukemia
• Helping treat cocaine addiction, schizophrenia, and gambling addiction
• Reducing lung cancer risk among smokers

More studies are needed.