opiates: semi-scientific questions

[ff3mwg]

1. I'm not dumb, I realize that codeine is much weaker than morphine, and that they're both considered opiates, but what is the main difference? Also, why is it that both morphine and codeine are present in pure opium?

2. How do morphine and codeine variations (dihydromorphone, dihydrocodeine, oxycodone, etc.) differ in effect on the body? Why do they each have distinct characterstics in terms of pain-killing, euphoria, and unwanted side-effects?

3. What causes that distinct "hit" from injected heroin? I know it has something to do with diacetylmorphine reaching the brain before it breaks down into morphine, but what's going on there exactly?

I'm pretty sure I've browsed erowid's resources enough to the point of memorization (just exaggerating ) but I'll give it another look.
-peace & good vibes

 

[Negro-kitty]

1. Opium contains numerous active alkaloids, including codeine and morphine as you know. Most plants that are psychoactive contain a variety of active chemicals -- the plant source for ephedrine, 'ma huang', for example, contains ephedrine as well as related alkaloids. Plants always contain a variety of different compounds because of their complex nature. If the plant is active in the human body at all, it is likely active in a variety of ways.

As for the difference between codeine and morphine, look here for a comparison of the two chemicals. Basically, codeine has a methoxy group (CH3O) coming off the benzene ring (that 6 sided ring on the top of the chemical) while morphine has an alcohol (OH) coming off the benzene ring. Otherwise the two molecules are the same. This chemical difference accounts for the difference in effects. Of course, in the human body codeine is converted into morphine by the liver, but this happens over time thus the different effects.


2. Opiates differ in effect because of different chemical substitutions. Opiates are modified versions of morphine (the -codone ending does not mean it is a 'codeine' variation). Different chemistry, different effects. There are three opiate receptors that are known -- delta, kappa, mu -- and different opiates act to different degrees at these receptors. In addition there are effects on other systems (norepinephrine, dopamine, serotonin) that while they are less significant also modify the effects. The exact chemical structure - pharmacologic effect relationships for each opiate are not yet well understood.

(Note: There are also a handful of 'opiods' like demerol (meperidine) and ultram (tramadol) which do NOT share the basic morphine structure and yet act on opioid receptors and have opiate-like effects.)

3. Don't really know the answer to this one.

 

[tramagesty]

[.




2. Opiates differ in effect because of different chemical substitutions. Opiates are modified versions of morphine (the -codone ending does not mean it is a 'codeine' variation). Different chemistry, different effects. There are three opiate receptors that are known -- delta, kappa, mu -- and different opiates act to different degrees at these receptors. In addition there are effects on other systems (norepinephrine, dopamine, serotonin) that while they are less significant also modify the effects. The exact chemical structure - pharmacologic effect relationships for each opiate are not yet well understood.
. [/B]

I have been led to believe that -codone is indicitive of a codeine variation, hydro and oxy being the hydrogentated and oxygenated ketones of codeine, respectivly.

Another question... Does the structure of Loperamide, which is a fentanyl analogue resemble morphine? Oh, and I forget...what receptor affects bowel motility?

 

[Negro-kitty]

I stand corrected re: -codone /codeine variation. For some reason I had thought that oxy and hydro-codone were altered at that same benzene position (at which morphine and codeine differ). This is not the case...that will teach me to always look up my structures!

Loperamide doesn't resemble morphine. It's pretty different from fentanyl too, structurally, but I can see a basic similarity at least.

I know that constipation ('bowel motility' hehe) results from the stimulation of opioid receptors in the GI tract...while activity at all three receptors can cause constipation, the mu receptor is most responsible for this effect.

 

[chugga chup]

in answer to question 3 - to reach the brain, drugs must cross the blood-brain-barrier (BBB) which is highly lipophylic. Heroin and its primary metabolite 6-monoacetylmorphine are much more lipophylic than morphine due to the presence of one and two acetyl groups respectively intead of two hydroxy groups - this allows them to pass into the brain more readily