Please note that the content of this book mainly consists of articles that are available from Wikipedia or other free sources online. Acetylcysteine (abbreviated ACC, NAC; formerly known as mercapturic acid) is a medication used to loosen mucus in respiratory diseases with thick sputum, such as bronchitis. The thick mucus stuck in the bronchi can be more easily coughed up after liquefaction (secretolysis). In addition to its medical use in pharmaceuticals, acetylcysteine is used as an ingredient in dietary foods, which are available in drugstores outside of pharmacies. Derivatives of N-acetyl-L-cysteine are breakdown products of the condensation products of glutathione with foreign substances in the human body and can be detected in urine.