Naltrexone (INN, BAN, USAN) is an opioid antagonist used primarily in the management of alcohol dependence and opioid dependence. It is marketed in generic form as its hydrochloride salt, naltrexone hydrochloride, and marketed under the trade names Revia and Depade. In some countries including the United States, a once-monthly extended-release injectable formulation is marketed under the trade name Vivitrol. Also in the United States, Methylnaltrexone Bromide, a closely related drug, is marketed as Relistor, for the treatment of opioid induced constipation. Naltrexone should not be confused with naloxone nor nalorphine, which are used in emergency cases of opioid overdose.