Naltrexone

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, an extended-release formulation is marketed under the trade name Vivitrol. It should not be confused with naloxone, which is used in emergency cases of overdose rather than for longer term dependence control.
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Naltrexone /nal·trex·one/ an opioid antagonist used as the hydrochloride salt in treatment of opioid or alcohol abuse. nal·trex·one n. [more]Naltrexone - Community and Resources

Noun
1. an oral antagonist against the action of opiates
(hypernym) narcotic antagonist