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NBME 23 Answers

nbme23/Block 1/Question#23

A 35-year-old man comes to the physician because of ...

Anticholinergic agent

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submitted by mcl(375),

To expand on this, what we think happens with Parkinson's disease (and parkinsonianism) is an imbalance between dopamine and acetylcholine. It makes more sense if you look at this diagram, paying particular attention to the indirect pathway. Loss of dopaminergic (DA) neurons from the substantia nigra (SNc) results in constant activation of those ACh secreting neurons, which ultimately results in inhibition of thalamus from initiating movements. Therefore, using anticholinergics help with parkinsonianism secondary to haldol.

mcl  Also, you don't wanna use sinemet since that would be counterproductive +1  
drzed  Whaaat? How could increasing levels of dopamine in a psychotic patient possibly be a bad thing? +  




Trihexphenidyl and Benztropine are antimuscarinics that can treat the resting tremor and rigidity of parkinsonism.

mousie  haloperidol induced Parkinson's... ? adding a anticholinergic can counter these adverse effects of the antipsychotic .. ? +2  
fulminant_life  @mousie yeah it balances the dopamine-cholinergic imbalance caused by the antipsychotics +  
kai  +So antipsychotics induce Extrapyramidal side effects which is drug induced Parkinson = low Dopamine High Ach, and you would treat this with anticholinergic (Benztropine).This is neurologic. +Antipsychotics also produce non-neurologic, systemic anti-cholinergic effects like dry mouth, sedation, hypotension etc +  




One of the tx strategies for drug induced Parkisonism or otherwise is to Curb excess cholinergic activity. Done by Benz-tropine, trihexyphenidyl (Antimuscarinic; improves tremor and rigidity but has little effect on bradykinesia in Parkinson disease). Park your Mercedes-Benz.