Opioid antagonist Opioid

opioid effects (adverse or otherwise) can reversed opioid antagonist such naloxone or naltrexone. these competitive antagonists bind opioid receptors higher affinity agonists not activate receptors. displaces agonist, attenuating or reversing agonist effects. however, elimination half-life of naloxone can shorter of opioid itself, repeat dosing or continuous infusion may required, or longer acting antagonist such nalmefene may used. in patients taking opioids regularly essential opioid partially reversed avoid severe , distressing reaction of waking in excruciating pain. achieved not giving full dose giving in small doses until respiratory rate has improved. infusion started keep reversal @ level, while maintaining pain relief. opioid antagonists remain standard treatment respiratory depression following opioid overdose, naloxone being far commonly used, although longer acting antagonist nalmefene may used treating overdoses of long-acting opioids such methadone, , diprenorphine used reversing effects of extremely potent opioids used in veterinary medicine such etorphine , carfentanil. however, since opioid antagonists block beneficial effects of opioid analgesics, useful treating overdose, use of opioid antagonists alongside opioid analgesics reduce side effects, requiring careful dose titration , being poorly effective @ doses low enough allow analgesia maintained.