Naltrexone is an opioid receptor 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 US, Methylnaltrexone Bromide, a closely related drug, is marketed as Relistor, for the treatment of opioid induced constipation.
Naltrexone should not be confused with naloxone (which is used in emergency cases of overdose rather than for longer-term dependence control) nor nalorphine. Using naloxone in place of naltrexone can cause far worse withdrawal symptoms; conversely, using naltrexone in place of naloxone in an overdose can lead to insufficient opiate antagonism and fail to reverse the overdose.
Read more about Naltrexone: Adverse Effects, Contraindications, Mechanism of Action, Structure and Pharmacokinetics