Opioids what's the difference ?

Ok so I was wondering why some opiates are stronger than others. For instance what makes oxycodone stronger than say hydrocodone? Its like opana and hydromorphone. What produces the euphoria and what makes one pill stronger in that aspect compared to another? When someone says 10 mg vicodin is equivalent to 7.5 mg of percocet , why do we even have 2 different meds? example, the doctor wants you to take 1 7.5 mg vicodin every 4-6 hours. Why not be prescribed 5mg percocet every 4-6 hours? See what I am getting at? What's mu receptors? Someone give me some cliffs on pain meds for pain relieve and recreational value. That is if someone is bored and wants to school me on a more in depth look at pharmaceutical meds. Thanks .

It's just the way they are made. Oxycodone /OxyContin are stronger than hydrocodone. We have 2 diff Meds bcuz some ppl respond differently to them. One that works great for u may not be great for someone else.

It depends on how strongly the drug binds to the receptor. Read this for more.

And subtle changes (swap an atom, bond, functional group, etc) effect the strength that the molecule binds to the receptor with. Look up the structure of a few - try codeine, morphine, and whatever other ones interest you. You'll see the shared common backbone, with small changes. For example, using the structures on Wikipedia, codeine has a methyl group (CH3) in the top left while with morphine it does not - this change reduces the potency a good deal between the two.

It gets much more in-depth but I'm trying to keep it simple, hope this helps give you an idea of whats going on.

Depending on the structure of the compound in question, there's a couple of things that will be effected if you change it. Morphine, for instance, is only poorly absorbed by mouth. Codeine is well-absorbed but does not bind to the opioid receptors very strongly and hence has a "ceiling" dose above which taking more won't have an effect. There's actually three opioid receptors - mu, delta, and kappa - mu is the one responsible for most painkilling effects and respiratory depression, delta and kappa opioid receptor are responsible for painkilling but also have their own strange side-effects (delta causes seizures in overactivation, kappa causes Salvia-type hallucinations) so generally people focus on the mu opioid receptor. You can twiddle little bits on e.g. the morphine molecule and change these properties.

In the early 1900s chemists were on a quest to find the ideal opioid, that didn't cause tolerance or side effects. They never found it but they did discover a bunch of chemical modifications of the morphine or codeine skeleton (or from other alkaloids in opium like thebaine) that were either more potent at the mu receptor, or were better absorbed orally, or didn't have a 'ceiling' effect. As a result we have lots of different compounds that suit different 'roles', e.g. oxymorphone is generally reserved for severe pain, hydrocodone for moderate intensity pain, oxycodone for oral opioid therapy due to high absorbtion, etc.

I will add that basically all these semi-synthetic opioids, i.e. hydrocodone, hydromorphone, oxycodone, and oxymorphone, have a ketone on C6, while morphine has an alpha-hydroxy group. Ketone's oxygen atom has a stronger negative charge on it than alcohol's oxygen and an electronegative group on C6 interacts with one lysine residue of mu opioid receptors. Lysine is an aminoacid with a positively charged side-chain, so generally the more electronegative the substituent at C6 is, the stronger the molecule binds to the receptor. Oxycodone and oxymorphone additionally both have a hydroxy group on the 14th position instead of a hydrogen, which further increases their affinity towards mu receptors, but mostly decreases affinity towards kappa receptors. So oxycodone/oxymorphone at an equivalent dose has a "cleaner" and more speedy feeling than morphine because it's more selective for mu receptors over kappa receptors. Kappa agonists are dissociative and somewhat sedative as well, that's why morphine may feel more sleepy. Many people thus prefer oxycodone to morphine, but I actually find morphine's high superior, it feels "deeper" and more spaced out.