Organophosphate Poisoning
Organophosphate Poisoning occurs due to exposure to organophosphates, these organophosphate compounds are used as commercial insecticides, in chemical warfare as nerve gases and are used as aerosols or dusts. They are rapidly absorbed through skin and mucous membranes or by inhalation.
Organophosphates are also used in ophthalmology (echothiopate is used to treat glaucoma).
Mechanism of toxicity
Acetylcholine is the neurotransmitter at the cholinergic synaptic areas. And acetylcholinesterase enzyme degrades acetylcholine following stimulation of a nerve. Organophosphates are acetylcholinesterase inhibitors and they form a stable irreversible covalent bond to the enzyme.
Organophosphates mediated inhibition of acetylcholinesterase causes acetylcholine to accumulate and results in initial excessive stimulation followed by depression.
In cholinergic junctions of the nervous system including postganglionic parasympathetic junctions (sites of muscarinic activity), autonomic ganglia and the neuromuscular junctions (sites of nicotinic activity) and certain synapses in the CNS all get affected by overstimulation by excessive acetylcholine.
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Signs and Symptoms
Muscarinic signs and symptoms
"Musc leaks from everywhere"
Remember this mnemonic SLUDGE, there is excessive secretions from everywhere in muscarinic overstimulation.
- S – salivation
- L- lacrimation
- U- urination
- D- defecation
- G- GI cramps
- E- emesis
Nicotinic signs and symptoms
"Nics give tension (hypertension), weakness and paralysis"
Remember this mnemonic MT WTF my BP is high, and Paralysis is happening.
- M-Mydriasis
- T-Tachycardia
- W-muscle weakness
- T-muscle twitching
- F-muscle fasciculation
- BP is high- hypertension
- Paralysis is happening – muscle paralysis
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Diagnosis
- most cases are clinically diagnosed.
- red blood cell cholinesterase levels and plasma cholinesterase levels can be done.
Treatment
- Remove clothes and wash the patient if skin exposure has happened.
- IV atropine- it is competitive inhibitor.
- IV pralidoxime- it reactivates acetylcholinesterase.
Further reference watch explanatory videos here https://www.youtube.com/watch?v=_cFmLd4TqT8
Revision for today https://creativemeddoses.com/topics-list/irritable-bowel-syndrome-stress-and-diarrhea/
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Case scenario
A 7-year-boy is brought to emergency department, he is lethargic and has excessive oral secretions and tearing. He has soiled his pants from urine and feces. His mother gave history of vomiting after a kid from school sprayed unidentified substance from his bottle while playing. The child was in good health before the incident. On physical examination constricted pupils are noticed, his blood pressure is 80/60 and heart rate is 46 beats/minute. Which drug is most likely to be effective in his condition?
- Intravenous Corticosteroid
- Intravenous Naloxone
- Intravenous Atropine
- Intravenous Edrophonium