This document discusses anticholinesterase poisoning from organophosphorus compounds. It covers the clinical features of organophosphorus poisoning including signs and symptoms due to excessive acetylcholine levels. Management includes atropine to block muscarinic receptors, pralidoxime as an enzyme reactivator, and supportive care. Atropine has anticholinergic effects and specific contraindications. Some synthetic drugs are similar to atropine but have more selective effects and fewer side effects for uses like mydriasis, gastrointestinal spasms, asthma, and parkinsonism.
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Understanding Organophosphorus Poisoning and Anticholinesterase Drugs
1. ⢠DR BADAR UDDIN UMAR
DRUGS ACTING ON THE ANS
ANTICHOLINESTERASE POISONING
ANTICHOLINERGIC DRUGS
LECTURE - 2
2. LEARNING OBJECTIVES:
At the end of this session the we shall be able to â
⢠Discuss the clinical features and drug treatment
of organophosphorus poisoning
⢠Explain the role of enzyme reactivators in
organophosphorus poisoning
⢠List and explain the adverse effects and
contraindications of atropine
⢠Discuss the aspects of pharmacokinetics, routes and
dosage of clinically important/ commonly used
drugs
3. ORGANOPHOSPHORUS POISONING
⢠Poisoning with organophosphorus
compounds (OPCs) may occur by â
⢠Accidental exposure during spraying
insecticides or in industry
⢠Suicidal poisoning
⢠Homicidal poisoning (rare)
⢠War gas exposure
4. OPC POISONING
⢠Acetylcholine esterase enzymes (AChE) of the
body will be destroyed
⢠Covalent phosphorus-enzyme bond
⢠Phosphorylation
⢠There will be massive (Acetylcholine) ACh
accumulation in the bodyâŚâŚ.ACh toxicity
5. ORGANOPHOSPHORUS COMPOUNDS
⢠Organophosphates are pentavalent phosphorus
compounds containing a labile group such as -
⢠Fluoride (in dyflos) or an
⢠Organic group (in parathion and ecothiopate)
⢠This group is released, leaving the serine hydroxyl
group (-SH) of the enzyme phosphorylated
6. ORGANOPHOSPHORUS COMPOUNDS
⢠The inactive phosphorylated enzyme is usually
very stable
⢠When phosphorylated by OPCs, AChE have no
ability to hydrolyze ACh and
⢠Recovery of enzymatic activity depends on the
synthesis of new enzyme molecules
⢠This may take weeks
⢠With ecothiopate, slow hydrolysis occurs over the course of a
few days, so that their action is not strictly irreversible
7. ORGANOPHOSPHORUS COMPOUNDS
⢠Dyflos and parathion are volatile non-polar
substances of very high lipid solubility
⢠Are rapidly absorbed through mucous membranes
and even through unbroken skin and insect cuticles
⢠Due to this they can be used as war gases or
insecticides
8.
9. SIGNS AND SYMPTOMS OF OPC POISONING:
ďą All s/s are due to âŚ.excessive level of Ach in the
body
ďą Muscarinic actions will lead to-
ďą Eye - Constricted pupils (Miosis), blurred vision, eye ache,
conjunctival congestion, brow ache
ďą Glands - Profuse Sweating, Salivation, Rhinorrhea &
Lacrimation
ďą ď GIT movement⌠Nausea, Vomiting, Diarrhea with
abdominal cramps
10. S/S OF OPC POISONING CONT.âŚ.
DUE TO MUSCARINIC ACTIONSâŚ..
ďą Genito urinary - Urgency for urination and
spontaneous voiding and penile erection (in severe
case)
ďą Bronchospasm, bronchial secretion Difficulty in
breathing
ďą Pulse rate/ Bradycardia
ďą Hypotension
ďą Collapse
12. S/S OF OPC POISONING FOR EASY REMEMBERING:
DUMBBELLSâŚâŚ stands for
⢠Diarrhea
⢠Urgency for Urination
⢠Miosis
⢠Bradycardia
⢠Bronchospasm
⢠Emesis
⢠Lacrimation
⢠Laxation and
⢠Salivation
13. MANAGEMENT OF OPC POISONING:
The therapy of organophosphate poisoning is known
by the catchy acronym - AFLOP:
ďą Atropine
ďą Fluids
ďą Oxygen
ďą Pralidoxime
14. MANAGEMENT OF OPC POISONING:
General measures:
ďą Termination of exposure by -
ďą Removal of clothes etc. that are contaminated
ďą Washing the whole body
ďą Gastric lavage
ďą Cleaning the airways for easy respiration
ďą Oxygen therapy and artificial respiration if needed
ďą IV fluid for correction of dehydration and shock
ďą IV Diazepam for convulsion
15. MANAGEMENT OF OPC POISONING:
Drugs used in OPC poisoning:
A) Atropine:
ďą It is the antagonist of Ach
ďą It will block the MR &
ďą Will prevent the effects of Ach
16. MANAGEMENT OF OPC POISONING:
Dose of atropine:
ďą1-2 mg IM or IV immediately
ďąRepeated 5-15 minâŚ..until signs of atropinization
ďą Dryness of mouth
ďą Reversal of miosis (mydriasis)
ďą HR: above 70/min
17. MANAGEMENT OF OPC POISONING:
B) Enzyme reactivator / regenerator
ďą Reactivate or regenerate AChE enzyme
ďą So AChE will be free again and metabolize ACh
Oximes -
ďą PAM (Pralidoxime) &
ďą DAM (Diacetylmonoxime)
18. MANAGEMENT OF OPC POISONING:
Oximes
ďą The oxime group (=NOH) has a high affinity for
phosphorous atom
ďą So, can hydrolyze the phosphorylated AChE enzyme
ďą Should be given within 12 hrs. of poisoning, after
that canât be reversed (stabilized by âagingâ)
27. ATROPINE-LIKE DRUGS
⢠Atropine has got wide-spread effect
⢠So, it produces many side-effects
⢠There are some Atropine-like synthetic drugs
⢠which are used clinically for different conditions
28. Atropine-like synthetic drugs
⢠These drugs have got more effect in that
specific purpose &
⢠has less side-effects than atropine
32. ATROPINE-LIKE MYDRIATICS:
⢠Atropine-like synthetic drug
⢠Duration of action: shorter than atropine
⢠Effect of atropine lasts for about 1 week
⢠Effects are like atropine but less side effects
33. ATROPINE-LIKE MYDRIATICS:
Used in eye for âŚ..
⢠Mydriasis for Funduscopic examination
⢠Accurate measurement of refractory errorâŚ. Specially
for un-cooperative patients & young children (ciliary
paralysis is required)
⢠Prevention of synechia (adhesion) formation in uveitis
& iritis
35. ATROPINE-LIKE MYDRIATICS:
⢠Now-a-days, antimuscarinics are less used for
opthalmoscopic examination if there is no need of
long lasting effect
⢠Alpha-adrenergic stimulants (e.g., phenylephrine)
are used for their short-lasting mydriatic effect,
specially for funduscopic examination
44. ATROPINE-LIKE ANTIPARKINSONIC DRUGS:
⢠Benztropine
⢠Orphenadrine
⢠Procyclidine
Selective effect in brain
⢠Decreases Ach effect in basal ganglia
⢠Decreases tremor, rigidity in parkinsonism
45. LEARNING OUTCOMES:
⢠At the end of this session the students will be able to â
⢠Discuss the clinical features and drug treatment of
insecticide (organophosphorus) poisoning
⢠Explain the role of enzyme reactivators and the
importance of âagingâ in organophosphorus poisoning
⢠List the adverse effects and contraindications of
atropine and explain the reasons of the same
⢠Discuss the aspects of pharmacokinetics, routes and
dosage of clinically important/ commonly used drugs
like atropine