Naloxone

naloxone (commonly sold under the brand names narcan and evzio) is a synthetic mu-opioid antagonist of the morphinan chemical class that is widely used to reverse the effects of an acute opioid overdose. naloxone is sold under the brand name narcan as a nasal spray and evzio as an auto-injector with voice instructions.

naloxone has been credited with saving an unprecedented number of opioid overdose victims. this is partially due to naloxone programs in several countries to give naloxone to people who use opioids along with the rapid deployment of naloxone by law enforcement agencies and emergency medical services. many emergency responders and law enforcement are trained to administer naloxone to reverse the effects of opioid overdoses immediately.

besides their use in emergency medicine, both naloxone and naltrexone have also been researched in the treatment of depersonalization disorder with promising results.

chemistry

on the chemical level, naloxone is similar in structure to many opiates and semisynthetic opioids. it is extremely similar in structure to the morphinan opioid oxymorphone. naloxone has an allyl group as opposed to a methyl group bound to the nitrogen, which has been shown to be a functional group substitution that often reverses the activity of opioid agonists and turns them into antagonist instead.

pharmacology

naloxone acts as a potent μ-opioid receptor inverse agonist. because of its high affinity for the μ-opioid receptor, it knocks other ligands out of the receptor. if naloxone is administered without previous administration of opioids, it has few biological effects, notably a lower pain threshold.

naloxone has two isomers, (+)naloxone and (-)naloxone, with the latter being active. the liver metabolizes naloxone. it has very low oral bioavailability, which is why it is administered intravenously, intramuscularly or intranasally. small amounts of naloxone are often added to opioids like buprenorphine and pentazocine to prevent abuse. this is because of the bioavailability difference; injecting the isolated ingredients from the pill will also inject naloxone.

naloxone has been noted to block a placebo based analgesic effect. for example, if an individual has been administered something that they were told was morphine and had an analgesic response to it, naloxone will block that response.

naloxone also has a lower affinity as an antagonist at the κ-opioid and δ-opioid receptors.