The antioxidant n-acetylcysteine (NAC) is emerging as a promising treatment for obsessive-compulsive disorder, offering new hope for the approximately 50 percent of adults with obsessive-compulsive disorder (OCD) who do not respond to customary treatments. Researchers have been accumulating evidence over the last few years that NAC, a derivative of the amino acid cysteine, available as an over-the-counter supplement, could help people with OCD. It’s also showing promise in the treatment of patients with the hair-pulling disorder trichotillomania and is being investigated as a treatment for compulsive gamblers and drinkers. However, research into NAC has been slow, in part because the drug, now available without a prescription, has limited commercial potential, according to Dr. Massimo Caroll, a pharmacologist and clinical toxicologist in the Department of Diagnostics and Public Health at the University of Verona in Italy. [Not as promising in the treatment of OCD in children….]