Opioids - toxicity / withdrawal

[Phloston]

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With respect to the third row down (opioids) on p. 495 of FA2012, could someone please explain the exact mechanism as to why each one of those specific side-effects are seen for both toxicity and withdrawal?

It just seems like there's a mix of both muscarinic-like agonistic and antagonistic effects occurring with both toxicity and withdrawal, and I haven't quite put together the whys yet.

Thanks again,

 

[Phloston]

Anybody?

 

[ijn]

According to Kaplan pharmacology it's too complex to be tested on for the MS2 level. There are a few fundamentals that I think are higher yield. Mu-opioid receptors stimulate G(i) complexes. High cAMP levels are associated with tolerance.

Miosis is specifically an antimuscarinic effect. Meperidine is an opioid noted for the lack of of antimuscarinic effects and has no miosis with intoxication.

The other side effects of opiates shouldn't necessarily classified as musarinic or antimuscarinic. They're mostly due to the central effects of mu-receptor interneurons. I don't know if we really have a solid grasp on the exact pathways other than seeing gross evidence of mu-stimulation. I'd be really suprised if the NBME tested on it. It's just something you have to memorize.

 

[An0MalY]

HAH i just so happen to have this article open: http://www.nejm.org/doi/full/10.1056/NEJMra1202561

 

[xenophila]

According to Kaplan pharmacology it's too complex to be tested on for the MS2 level. There are a few fundamentals that I think are higher yield. Mu-opioid receptors stimulate G(i) complexes. High cAMP levels are associated with tolerance.

Miosis is specifically an antimuscarinic effect. Meperidine is an opioid noted for the lack of of antimuscarinic effects and has no miosis with intoxication.

The other side effects of opiates shouldn't necessarily classified as musarinic or antimuscarinic. They're mostly due to the central effects of mu-receptor interneurons. I don't know if we really have a solid grasp on the exact pathways other than seeing gross evidence of mu-stimulation. I'd be really suprised if the NBME tested on it. It's just something you have to memorize.

Isn't miosis related to cholinomimetic/cholinergic agonist/cholinesterase inhibitor response? Antimuscarinic would be mydriasis... am I missing something?

 

[Phloston]

Isn't miosis related to cholinomimetic/cholinergic agonist/cholinesterase inhibitor response? Antimuscarinic would be mydriasis... am I missing something?

Yeah. I was going to let it slide before as I had assumed he just made a typo, but yes, miosis is muscarinic and mydriasis anti-muscarinic.

 

[ijn]

Wow, yeah. Man, that kind of stuff slips from your brain so quickly. 😆

 

[Morsetlis]

According to Kaplan pharmacology

Ah mah gawd I finally remember where your avatar comes from 🙂