Acetylcysteine, also known as N-acetylcysteine (NAC), is a medication that is used to treat paracetamol overdose and to loosen thick mucus in individuals with chronic bronchopulmonary disorders like pneumonia and bronchitis. It has been used to treat lactobezoar in infants. It can be taken intravenously, by mouth, or inhaled as a mist. Some people use it as a dietary supplement.Common side effects include nausea and vomiting when taken by mouth. The skin may occasionally become red and itchy with any route of administration. A non-immune type of anaphylaxis may also occur. It appears to be safe in pregnancy. For paracetamol overdose, it works by increasing the level of glutathione, an antioxidant that can neutralise the toxic breakdown products of paracetamol. When inhaled, it acts as a mucolytic by decreasing the thickness of mucus.Acetylcysteine was initially patented in 1960 and came into medical use in 1968. It is on the World Health Organizations List of Essential Medicines. It is available as a generic medication and is inexpensive.The sulfur-containing amino acids cysteine and methionine are more easily oxidized than the other amino acids. Uses
Paracetamol overdose
Intravenous and oral formulations of acetylcysteine are available for the treatment of paracetamol (acetaminophen) overdose. When paracetamol is taken in large quantities, a minor metabolite called N-acetyl-p-benzoquinone imine (NAPQI) accumulates within the body. It is normally conjugated by glutathione, but when taken in excess, the bodys glutathione reserves are not sufficient to deactivate the toxic NAPQI. This metabolite is then free to react with key hepatic enzymes, thereby damaging liver cells.
Addiction
Evidence to date does not support the efficacy for N-acetylcysteine in treating addictions to gambling, methamphetamine, or nicotine. Based upon limited evidence, NAC appears to normalize glutamate neurotransmission in the nucleus accumbens and other brain structures, in part by upregulating the expression of excitatory amino acid transporter 2 (EAAT2), a.k.a. glutamate transporter 1 (GLT1), in individuals with addiction. While NAC has been demonstrated to modulate glutamate neurotransmission in adult humans who are addicted to cocaine, NAC does not appear to modulate glutamate neurotransmission in healthy adult humans. NAC has been hypothesized to exert beneficial effects through its modulation of glutamate and dopamine neurotransmission as well as its antioxidant properties. Microbiological use
Acetylcysteine can be used in Petroffs method of liquefaction and decontamination of sputum, in preparation for recovery of mycobacterium. It also displays significant antiviral activity against the influenza A viruses.Acetylcysteine has bactericidal properties and breaks down bacterial biofilms of clinically relevant pathogens including Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecalis, Enterobacter cloacae, Staphylococcus epidermidis, and Klebsiella pneumoniae. Other uses
Acetylcysteine has been used to complex palladium, to help it dissolve in water. This helps to remove palladium from drugs or precursors synthesized by palladium-catalyzed coupling reactions. N-actelylcysteine can be used to protect the liver. Side effects
The most commonly reported adverse effects for IV formulations of acetylcysteine are rash, urticaria, and itchiness. Up to 18% of patients have been reported to experience anaphylaxis reaction, which are defined as rash, 
hypotension, wheezing, and/or shortness of breath. Lower rates of anaphylactoid reactions have been reported with slower rates of infusion.