Autonomic Nervous Systems
Mechanism of action of PAM/pralidoxime is (LQ)
|A||Synthesis of cholinesterase|
|B||Reactivation of cholinesterase|
|C||Inhibition of cholinesterase|
|D||None of the above|
a. Oximes are used to restore neuromuscular transmission in case of organophosphate anti-ChE poisoning.
b. The phosphorylated ChE reacts very slowly or not at all with water.
c. However, if more reactive OH groups in the form of oximes are provided, reactivation occurs more than a million times faster.
d. Pralidoxime (2-PAM) has quaternary nitrogen: attaches to the anionic site of the enzyme which remains unoccupied in the presence of organophosphate inhibitors.
e. Its oxime end reacts with the phosphorus atom attached to the esteratic site: the oxime-phosphonate so formed diffuses away leaving the reactivated ChE.
f. It is ineffective as an antidote to carbamate anti-ChEs (physostigmine, neostigmine, carbaryl, propoxur) in which case the anionic site of the enzyme is not free to provide attachment to pralidoxime.
g. It is rather contraindicated in carbamate poisoning, because not only
h. it does not reactivate Carbamalyte enzyme, it has weak anti-ChE activity of is own.