Naltrexone, sold under the brand names Revia and Vivitrol among others, is a medication primarily used to manage alcohol dependence and opioid dependence. In opioid dependence, it should not be started until people are detoxified. It is taken by mouth or by injection into a muscle. Effects begin within 30 minutes. A decreased desire for opioids however may take a few weeks.
Side effects may include trouble sleeping, anxiety, nausea, and headaches. In those still on opioids, opioid withdrawal may occur. Use is not recommended in people with liver failure. It is unclear if use is safe during pregnancy. Naltrexone is an opioid antagonist and works by blocking the effects of opioids, both those from inside and outside the body.