Naloxone (Narcan) – inj. – pure antagonist – This is available only as an IV injection, it doesn’t work orally.
This blocks the endorphin receptor and reverses opiate toxicity effects. But this antagonist is so unique on your list. Not only it blocks the receptor but it can pull the endorphin off the receptor sitting on the receptor and replace it. So it displaces opiates on receptors. So how quickly does this antidote work? Almost instantly.
If a patient comes into ER that isn’t breathing. Within 1-2 minutes they wake up like nothing has happened to them. The drawback is that it’s extremely short acting and it’s out in 30 minutes. If a person OD’d on a long acting drug like heroin, they may go back to not-breathing in 30 minutes and you may have to repeat the dose. This is also utilized post-operatively because you want the patient to breath.
What would happen if you gave this drug to an addict? Naloxone precipitates withdrawal. If you give them this drug and they’re an addict (meaning every endorphin receptor in their body is geared to being stimulated), this antidote will blocks every receptor (no stimulation possible) and they will go into severe, immediate withdrawal.