partial agonist with full agonist or RI

[QUARE]

I can't remember if partial agonist mixed with fulll agonist or a reuptake inhibitor drug cause increase effect or decrease effects due to there ceilling effect.

 

[endotropic]

I can't remember if partial agonist mixed with fulll agonist or a reuptake inhibitor drug cause increase effect or decrease effects due to there ceilling effect.

Hmm I'm not sure if I'm understanding you right, but if you take a partial agonist and a full agonist for the same receptor, the partial will prevent the full from producing its full effect. When you combine a partial agonist and a reuptake inhibitor the net effect will depend on which receptor and neurotransmitter each is affecting.

 

[QUARE]

ok thanks, yes you understood correctly.

 

[sekio]

Hmm I'm not sure if I'm understanding you right, but if you take a partial agonist and a full agonist for the same receptor, the partial will prevent the full from producing its full effect.

You have to compare the Ki (binding affinity) of the drugs in question.

Say you have opioids. Morphine is a full agonist with "low" affinity, buprenorphine a partial agonists with higher affinity, fentanyl is a higher affinity agonist, naltrexone (not naloxone) an antagonist that's even higher. If you're on morphine and you take buprenorphine, the morphine is displaced by the partial agonist. If you are on bupe and you take naltrexone, bupe is displaced. If you're on bupe and you take fentanyl, bupe is displaced.

Partial agonist, full agonist etc, is unrelated.

 

[endotropic]

You have to compare the Ki (binding affinity) of the drugs in question.

Say you have opioids. Morphine is a full agonist with "low" affinity, buprenorphine a partial agonists with higher affinity, fentanyl is a higher affinity agonist, naltrexone (not naloxone) an antagonist that's even higher. If you're on morphine and you take buprenorphine, the morphine is displaced by the partial agonist. If you are on bupe and you take naltrexone, bupe is displaced. If you're on bupe and you take fentanyl, bupe is displaced.

Partial agonist, full agonist etc, is unrelated.

That's all relative to dose though. If you take each at equipotent doses they'll compete for the receptor equally, due to the higher concentrations of the lower affinity compounds. It's possible to take so much morphine that a standard dose of naltrexone couldn't out-compete it.

 

[QUARE]

So would a drug that have binding affinity of 1nM but the dose is 1mg would it be enough to displace a drug that have affinity of 10nM and dose is 10mg or would they be in competition.

Im not sure though if binding affinity is linear or quadratic.

 

[endotropic]

So would a drug that have binding affinity of 1nM but the dose is 1mg would it be enough to displace a drug that have affinity of 10nM and dose is 10mg or would they be in competition.

Im not sure though if binding affinity is linear or quadratic.

If you assume that 100% of each drug makes it into the blood stream then neither would completely displace the other. They would compete equally for the receptors because of the higher concentration of the lower affinity drug.

You have to take bio-availability into account too though. In reality 100% of the dose doesn't actually make it into the blood stream, and that will vary from drug to drug.