Pinpoint pupils

[hammerpcp]

There are two opiod drugs that do not cause pupil constriction: demerol and talwin. Does anyone know why this is?

[becksdad]

This is just a semi-educated guess, but I think that Talwin (Pentazocine) is actually an opiod antagonist with some agonist properties. My guess would be that its antagonistic properties are what keeps it from constricting pupils. Demerol, I'm not sure, although I know it is entirely synthetic.

Actually, I'm not sure why I posted this, since I really don't know (bored?). But now I will do a little research on it, and read what the real experts have to say on here.

[AZCEP]

For Demerol it does have an effect on pupillary constriction, but it requires a higher dose to accomplish it. The pupils are another smooth muscle site that Demerol doesn't have a great effect on.

[Asysin2leads]

Because God wills it. Next question.

[DwayneEMTP]

Actually, I'm not sure why I posted this, since I really don't know (bored?).

Oh Lord....that was funny....

Dwayne

[hammerpcp]

Because God wills it. Next question.

#-o How could I have missed that?!

[OVeractiveBrain]

Opiate receptors in the brain respond to naturally occuring opiods (opiates) and synthetic opiods (the difference between opiod and opiate is often overlooked and is commonly inconsequential).

There are three types of opiod receptors in the brain, that produce different effects in different ways.

Mu-Receptors are located in the Spinal Trigeminal Nucleus, Caudate and Geniculate Nuclei, the Thalamus and The spinal cord. These are responsible for the primary effects we see with the administration of opiods - analgesia, euphoria, respiratory depression, nausea, GI inhibition and miosis (pupillary constriction).

Kappa-Receptors produce modest forms of analgesia dysphoria, miosis and repiratory depression when activated on their own and are found in the basal ganglia, nucleus accumbens, hypothalamus, spinal cord and periphery. These can be seen as "adjunct receptors" to the Mu

Delta Receptors are poorly understood and are located in the limbic system

Morphine strongly binds to Mu receptors and partially to kappa receptors, but not to delta receptors.

Demerol strongly binds to Mu receptors but NOT kappa receptors.

Fentanyl and Methadone are in the same class of binding affinity for Mu receptors as Demerol.

Talwin is a mixed agonist / antagonist that binds only to Kappa receptors, and not to Mu receptors.

These differences are largely in part due to their gross differences in chemical structure.

That being said, morphine is the most likely of the three to demonstrate side effects, especially miosis and is nearest to most naturally produced opiates in the body. Heroin is a simple chemical transformation of morphine. This is why we see miosis most commonly with morphine administration.

All this being noted, Demerol WILL produce pupillary constriction, given a sufficient dose. Its effects on membrane dryness or GI tract mobility may be more potent than its effects on the pupils, but it will cause pupillary constriction. The key thing to remember is that the administration of an opiod doesnt magically effect the brain, nor are all opiods equal in chemical structure, solubility or explicit binding affinity. This is why we will more likely see miosis with fentanyl or methadone than with demerol. But liek demerol, it takes a fairly sufficient dosage of methadone to cause miosis and respiratory depression. Keep in mind demerol is only 1/50th as potent an analgesic as morphine.

Talwin is an agonist/antagonist. It binds and activates opiod receptors, but then prevents them from being reactivated. Given its antagonist properties, we should not see signs of opiod overdose with talwin, unless an extremely high dosage is used.

IN SHORT:

The differences in chemical structure contribute to alterations in solubility, binding affinty and receptor options for binding. This in turn results in different presentations between opiods. Some induce pupillary constriction more than GI immobility, while others produce mucous drying over nausea. The point is, that given a sufficient amount of any opiod both miosis and respiratory depression (the things we medics really look at for in diagnosing an opiod overdose) can be produced. It helps to have a lab and urine analysis handy to make real hard-cased diagnoses.

-OveractiveBrain

[windsong]

This is just a semi-educated guess, but I think that Talwin (Pentazocine) is actually an opiod antagonist with some agonist properties. My guess would be that its antagonistic properties are what keeps it from constricting pupils. Demerol, I'm not sure, although I know it is entirely synthetic.

Actually, I'm not sure why I posted this, since I really don't know (bored?). But now I will do a little research on it, and read what the real experts have to say on here.

________________________________________________________________________________

________________________

I remember when the medics arrived at the bowling alley one year and they mentioned that this guys pupils were semi-dilated, ok what the heck is semi dialted?

And I remember him going through his drug box and the emt mentioned the name, talwin.

Becksdad, an educated guess is better than none at all. :wink:

[becksdad]

windsong, most of my guesses are semi-educated at best!!

[windsong]

:thumbleft: ok if you say so :wink: I believe ya.