The way I understand receptors are usually first come first served.
If someone has taken drugs that have bound to the receptor how does the narcan then bind to the receptor and revive someone?
In: Chemistry
Receptors have preferences for different things that can bind to them. The more a receptor would prefer to bind to one substance, the more likely it is to kick off another substance. It’s kind of like if you’re offered a Diet Coke — you like Diet Coke so you’ll drink it, but you **really** like Dr. Pepper. If someone comes along and offers you a Dr. Pepper, you’ll toss the Diet Coke to the side and start drinking the Dr. Pepper instead. The various receptors in your body that opioids bind to have a much stronger preference for Narcan than the opioid drugs
Narcan is a ***competitive antagonist*** for the opioid receptors, which means it binds to the receptors very strongly (*competitive*) without activating the receptor (*antagonist* vs *agonist*). Basically, it binds to part of the opioid receptor strongly enough that it tends to stay there even if another molecule comes along that could also bind to that part of the receptor. And because the receptor won’t do anything unless the whole thing is correctly bound, the narcan blocks opioid agonists like heroin from binding to the receptors and actually activating them. So it very quickly reverses the fatal effects of an opioid overdose but doesn’t hurt you if you’re not ODing.
Pharmacological activity pretty much looks like if you got a bunch of people together, randomly attached strong magnets all over their bodies, recorded them dancing shoulder-to-shoulder in a packed club for a night, and then played the footage at 100x speed. They get stuck together and separate constantly, but overall the ones who stayed stuck together in the same configuration for the longest periods of time were the ones who had their magnets lined up correctly (he’s got two + magnets on his arms, she’s got two – magnets on her back, etc.)
Naloxone has stronger affinity to the receptor so it will out compete opioids in the receptor, displacing them and prevent further binding, thus reversing the OD.
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