management of op poisoning-definitive treatment
DESCRIPTION
TRANSCRIPT
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DEFINITIVE TREATMENTOF
ORGANOPHOSPHORUS POISONING
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Atropine
Cholinesterase reactivators (Oximes)
Drugs used in definitive treatment:
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(a)ATROPINE
Anti cholinergic drug.
Objective : To block the muscarinic receptors until the organophosphate is metabolised away from the body.
Atropine : Adult dose : 2-5mg i.v. repeated every 5 min doubling the initial dose.
Children : 0.05-0.1mg/kg
Given till signs of atropinization appear.
Continued treatment: maintenance dose (30% of atropinization dose) for 1-2 weeks.
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(b)CHOLINESTERASE REACTIVATORS
Oximes are used to restore neuromuscular transmission.
If more reactive OH groups in the form of oximes (Generic formula R-CH=N-OH) are provided reactivation occurs more faster.
Eg: Pralidoxime ( 2-PAM)
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Action of Pralidoxime (2-PAM)Attaches to the anionic site of the enzyme.Oxime end reacts with the phosphorus atom
attached to the esteratic site.Oxime-phosphonate form and diffuse away.Reactivated ChE remain. Treatment should be started within 24 hours
before the phosphorylated enzyme undergoes ‘Aging’ and become resistant to hydrolysis.
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It is ineffective to carbamate poisoning as in that case the anionic site of the enzyme is not free.
It is rather contraindicated because it has weak anti-ChE activity of its own.
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Injected i.v. slowly in a dose of 1-2g.
Doses may be repeated according to need.
Use of oximes in OP poisoning is secondary to that of Atropine.
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OTHER OXIMES:
Obidoxime: more potent than pralidoxime
Diacetyl-monoxime (DAM): Lipophilic; so if the OP poisoning symptoms are more central DAM is used as it can cross the blood brain barrier.