Depolarizing NM blockers

[vkhullar]

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I have a q - in Phase II of depolarizing muscular blockers, you have no response to ACh, then how do ACHEi reverse it?

I understand how in phase I they augment the effect of succinylcholine but I do not comprehend why they would be used to reverse the block. Could someone please explain.

 

[drizzt3117]

I have a q - in Phase II of depolarizing muscular blockers, you have no response to ACh, then how do ACHEi reverse it?

I understand how in phase I they augment the effect of succinylcholine but I do not comprehend why they would be used to reverse the block. Could someone please explain.

I think in phase 2 they can come off, the ach-I will just make more ach around to replace it as soon as the pseudocholinesterase takes it off.

 

[vkhullar]

I think in phase 2 they can come off, the ach-I will just make more ach around to replace it as soon as the pseudocholinesterase takes it off.

Well I still don't understand.

Let reason this :

Phase 1 : Succinylcholine causes excitation ==> fasiculation ==> ACHEi increase ACh potentiating the effect so you read desensitization faster. I get this.

Phase 2: Well your receptors are already desensitized, how will adding/keeping the AChE inhibitors ==> Increase in ACh change the desensitized receptor to become sensitized again.

What do you mean by they come off - why does FA say they help with resensitizing the receptor. I am so confused.

 

[lord_jeebus]

I don't think neostigmine "resensitizes" the receptor; but desensitization can be overcome with increased synaptic ACh, as the nicotinic receptors are still responsive, just less so. I would guess that by the time the neostigmine has worn off, the desensitization has also spontaneously resolved.

This is somewhat speculation on my part, and my understanding is that Phase II block is not completely understood.

 

[drizzt3117]

Succinylcholine is an agonist, unlike organophosphates, so it depolarizes

Well I still don't understand.

O
Phase 1 : Succinylcholine causes excitation ==> fasiculation ==> ACHEi increase ACh potentiating the effect so you read desensitization faster. I get this.

Phase 2: Well your receptors are already desensitized, how will adding/keeping the AChE inhibitors ==> Increase in ACh change the desensitized receptor to become sensitized again.

What do you mean by they come off - why does FA say they help with resensitizing the receptor. I am so confused.