Narcan and Vivitrol (injectable formulations of naloxone) Naloxone basically has the same pharmacological effects as naltrexone, but it is shorter acting, and thus makes it. Article on Possibly Preventing HPTA Shut Down Using Naloxone and Naltrexone. We forget that the pituitary is susceptible to the same degradation and. Like naloxone (Narcan), which was developed by the same people four years earlier as the antidote for opiate overdoses, naltrexone is an opiate blocker. Naloxone is a drug used to counter the effects of this is that these endorphins operate on the same. Diprenorphine - Nalorphine - Naloxone - Naltrexone - Nalmefene.