The hydrochloride salt of naloxone, a thebaine derivate with opioid antagonist activity. Naloxone binds to opioid receptors in the CNS in a competitive manner, reversing or inhibiting characteristic opioid effects, including analgesia, euphoria, sedation, respiratory depression, miosis, bradycardia, and physical dependence. This agent binds to mu-opioid receptors with a high affinity, and a lesser degree to kappa- and gamma-opioid receptors.