Naltrexone is a prescription opioid antagonist drug that is used to treat opioid dependence. It has no euphoric effect but acts to block the effects of opioids. Naltrexone is also prescribed for treatment of alcohol dependence by reducing the effects of alcohol on the body and diminishing cravings overtime.

It is taken orally as a tablet, by subcutaneous implants (a pellet or other container inserted under the skin that slowly releases the drug) or by intramuscular injection in a slow-release suspension. Naltrexone is most effective in patients who are highly motivated and who have good social support...