N-acetyl cysteine (NAC) is used by the body to create antioxidants. Antioxidants are vitamins, minerals, and other nutrients that protect and repair cells from damage. NAC can be taken as a supplement or as a prescription drug.

As a prescription drug, doctors use NAC to treat acetaminophen overdose. It can also help break down mucus in people with certain lung diseases such as chronic bronchitis. As a supplement, some people use NAC to try to protect the liver. There is evidence that certain medications can help prevent bladder or neurological damage caused by them.