Naloxone is an opioid antagonist, in the model of naltrexone, that is used to combat the effects of heroin or morphine overdose in addicts. Naloxone has a much greater affinity to opioid receptors than either of those drugs, and so will actually displace the drug molecule at the receptor site, blocking its action on the neuron. The unfortunate result of this is that the addict is suddenly thrust into severe withdrawal syndrome, since the drug has been abruptly and totally blocked from all action everywhere through their body.

Not only does naloxone displace heroin and morphine at the brain's receptor sites, it will also keep endorphins and other endogenous opioid transmitters from functioning properly. An experiments was conducted on women undergoing natural childbirth, where a control group underwent the procedure as normal and another group was administered naloxone before delivery. The women who received naloxone rated their subjective pain experienced at a much higher level than the women in the control group did. (not that I know, but from reputation, one would think the pain of childbirth would be more than enough, thanks! this is price of science I suppose.)

Clinics have begun handing out naloxone kits to addicts in major cities. These kits are intended for emergency use on overdose patients in an environment where professional medical attention is unfeasible. It is documented that lives have been saved as a result of this policy of distributing naloxone kits.1