an agent which acts as an antagonist at opioid receptors. Typically, opioid antagonists are synthetic sub=products of morphine which, as an outcome of structural alterations within the molecule, bind to opioid receptors but don't generate the impacts of euphoria, respiratory depression, or analgesia which are viewed with opioid agonists. Commonly referred to as narcotic antagonist.
OPIOID ANTAGONIST: "Nalorphine is an example of an opioid antagonist."
