eli5: If our own endogenous opioids are stronger than morphine then why do people need pain killers?

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For example beta-endorphin which is produced by our bodies during pain, stress, exercise, pleasure, is 18 to 33 stronger than morphine according to https://en.m.wikipedia.org/wiki/Beta-Endorphin under “Pain Management” so why would we even need pain killers?

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First of all morphine isn’t going to replace/negate beta-endorphin. It’s just going to provide pain relief on top of it.

Second, it’s likely being measured by volume or number of molecules that can attach to receptors or something. If beta endorphin is 33 times stronger, it’s the same strength as 33 times as much morphine.

Also, morphine is actually a fairly weak opiate iirc. Dilaudid and fentanyl are supposedly where it’s at.

Your body produces just the minimal amount of beta endorphin as needed to dull pain to the “appropriate” amount. And your body doesn’t want to completely kill pain! After all, pain serves a purpose – making you aware that something is wrong, and the more severe the injury, the more pain you feel to make sure you don’t ignore it and cause further harm.

Of course, sometimes we want to override our body’s pain pathways and dull pain further, especially once we’re already doing all we can to treat the underlying cause. So why not just take beta endorphin then? Well there are a few problems. Beta endorphin is a polypeptide (ie small protein, coded for by a gene), which means it’s not easily made artificially in a lab, at least before CRISPR and other gene editing techniques, and also your body breaks down most proteins you ingest into their constituent amino acids during digestion. So it likely wouldn’t be active at all taken orally. Morphine occurs naturally in poppies at a high enough concentration to be directly useful as a painkiller.

Vodka is about 8 times stronger than beer. And yet you’ll get a lot more drunk from drinking 10 beers than from drinking a single shot of vodka.

Beta-endorphins being stronger than morphine does you precisely zero good if your body refuses to release any more of those endorphins while you’re in pain. And that’s often the case. Our bodies didn’t evolve to suppress pain. That would defeat the purpose of having pain in the first place. It’s meant to be a warning signal, not to be ignored. When pain is severe or long-lasting, your body may suppress is somewhat, but never completely and often not enough for comfort.

And that’s why we use pain-killers: since the body won’t shut off the pain of its own accord, we need to send an external signal to do the job instead. And that’s where things like morphine come in. Now, if we could somehow use or mimic the endogenous opioids and use them as a painkiller, perhaps that might be more effective than the painkillers we currently have. I’m not a pharmacologist but I imagine this is simply not currently possible with the knowledge and technology that we have. E.g. maybe we have no way of synthesizing beta-endorphins, or maybe we do but we have no way of administering them (e.g. because they won’t cross the blood-brain barrier or something), or maybe the problem is that they have more side effects when administered in the kind of doses required for adequate pain relief, and so forth.