About Naloxone A ?-opioid receptor competitive antagonist, Narcotic antagonist. Mechanism of Action of Naloxone Naloxone is a pure semisynthetic opiate antagonist. It acts as a competitive antagonist at mu, kappa and delta opiate receptors in the CNS. It reversibly and completely blocks all the opioid receptors (mu, kappa and delta). Indications for Naloxone 1.Opioid poisoning 2.Opioid-induced respiratory depression