NB F2: Muscar agonists

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NB F2: Muscar agonists

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Musuq
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10/21/06 - 11:47 AM

1. A 35-year-old woman has a 1-month history of intermittent ptosis and diplopia. She has limited abduction and elevation of the right eye and fatigable ptosis of the left. After 2 days of pyridostigmine therapy, her ocular symptoms resolve. One week later she develops nausea and abdominal cramping that are most severe 30 minutes after her dose of pyridostigmine. Administration of which of the following medications is most likely to ameliorate her gastrointestinal symptoms?

A. Atropine

B. Bromocriptine

C. Neostigmine

D. Phenoxybenzamine

E. Propranolol

fongch
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10/21/06 - 09:24 PM

A. Antropine can block the excessive muscarinic stimulation and relieve spasm

fongch
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10/21/06 - 09:25 PM

fongch wrote:
A. Atropine can block the excessive muscarinic stimulation and relieve spasm

Musuq
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10/22/06 - 11:21 PM

yes, ATROPINE is a muscarinic blocker so it would reverse the G.I. symptoms we are getting as a side effects from giving Pyridostigmine (a cholinomimetic, AchE inhibitor) to this patient with Myastenia Gravis, but my doubt was this...

... If i am treating a patient with Myasthenia Gravis, an autoimmune disease with autoAb (Type II H.S. Reaction) against Ach receptors; if I am treating her with Pyridostigmine to improve her muscle weakness and fatigue, will it be valid to stop the treatment with anti-cholinesterase (Cholinomimetic) and now give Anti-cholinergics as Atropine (Musc Blocker)? Should I just think about the side effects and dismiss the main disease?

I was thinking maybe Neostigmine could be less harmful that pyridostigmine and still help the MG???

It may sound like a silly doubt but that was my confusion approaching this qs.

Somebody?

Revenged
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10/24/06 - 02:31 PM

Musuq wrote:
I was thinking maybe Neostigmine could be less harmful that pyridostigmine and still help the MG???

Perhaps that's true... but the question wanted to know what you'd give to stop the abdominal pain...

and if you were to stop the over activation of the parasympathetic system causing the abdominal cramps, you'd need to block the muscarinic receptors with atropine...

If you gave the patient neostigme (another anti-cholinesterase) it would increase the binding of ACh to mAChRs, increase the parasympathetic responce and cause the abdominal cramps to get worse...

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