Definition of naltrexone in US English:



  • A synthetic drug, similar to morphine, which blocks opiate receptors in the nervous system and is used chiefly in the treatment of heroin addiction.

    • ‘Thus, the researchers proposed the hypothesis that alcohol releases endogenous opioids and that naltrexone blocks the opioid receptor.’
    • ‘In addition, this research group also determined that naloxone, an opiate antagonist similar to naltrexone, prevented the action of both marijuana and heroin on dopamine transmission.’
    • ‘The use of the opiate antagonist, naltrexone in the treatment of autism is reasonable since it antagonizes endogenous opiate receptor activity.’
    • ‘Small studies have suggested that the opiate antagonist naltrexone is effective as an adjuvant therapy for treating alcohol addiction.’
    • ‘Long-term opioid therapy for chronic pain or heroin dependence is a contraindication for naltrexone because the drug could precipitate severe withdrawal syndrome.’
    • ‘It is working on a version containing naltrexone, an opiate antagonist that would block oxycodone's euphoric effects once the pill was crushed.’


1970s: from a contraction of N-al(lylnoroxymorph)one (see naloxone), with the insertion of the arbitrary element -trex-.