A Nice Pharma Question

2527 Views 5 Replies 5 Participants Last post by 1TA2B, Mar 3, 2011

sunny

Discussion Starter · Mar 3, 2011

A 32 yr old man comes for weakness and blurred vision. He states that these symptoms become progressively worse throughout the day and improve with rest. On examination ptosis and weakness of limb muscles seen on repetitive testing. If pharmacotherapy is indicated, the most appropriate treatment is a drug with which of the following mechanisms ??
A. Carbamylation of Acetylcholinesterase
B. Dephosphorylation of Acetylcholinesterase
C. Direct muscarinic receptor agonist
D. Direct muscarinic receptor antagonist
E. Direct nicotinic recpetor agonist
F. Phosphorylation of Acetylcholinesterase

Reasoning must with ans.

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jorgemorales

· #2 · Mar 3, 2011

I'll say it's A. Carbamylation of Acetylcholinesterase.
Most reversible acetylcholinesterase inhibitors are carbamates (remember insecticides).
I know organophosphorates irreversible phosphorylate acetylcholinesterase, so it's not F, and that for me, would also discard B dephosphorylation.

Veeery nice question indeed. Please correct me if i'm wrong with full explanations.

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sunny

Discussion Starter · #3 · Mar 3, 2011

jorgemorales said:
I'll say it's A. Carbamylation of Acetylcholinesterase.
Most reversible acetylcholinesterase inhibitors are carbamates (remember insecticides).
I know organophosphorates irreversible phosphorylate acetylcholinesterase, so it's not F, and that for me, would also discard B dephosphorylation.

Veeery nice question indeed. Please correct me if i'm wrong with full explanations.

You re right. This is a case of myasthenia gravis. Two of them most common drugs used in this are neostigmine and pyridostigmine ( carbamates ) both of which act by carbamylating the acetylcholinesterase enzyme.
In severe cases of MG the above drugs are combined with prednisone.
I hope its clear enough.
Good Luck !! :happy:

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apx85

· #4 · Mar 3, 2011

Not Sure

The patient presents with signs of Myesthenia Gravis, which is treated by acetylcholinesterase inhibitors (the "stigmines") but I'm not sure as to their exact mechanism. I would guess F, phosphorylation but it could be A or B as well.

Good question!

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