Learning Objective
Identify the muscarinic and nicotinic toxic effects of AChE inhibitor overdose and know the key management strategies.
Mechanism
- Excess ACh accumulation → overstimulation of muscarinic and nicotinic receptors
- Causes both peripheral and central cholinergic symptoms
Muscarinic Effects: “DUMBBELSS”
| Letter | Effect |
|---|---|
| D | Diarrhea |
| U | Urination |
| M | Miosis |
| B | Bradycardia |
| B | Bronchoconstriction |
| E | Emesis |
| L | Lacrimation |
| S | Salivation |
| S | Sweating |
Other: CNS stimulation (confusion, seizures)
Nicotinic Effects
- Skeletal muscle fasciculations → paralysis
- CNS stimulation → anxiety, seizures
Management
| Target | Drug / Action |
|---|---|
| Muscarinic symptoms | Atropine (competitive muscarinic antagonist) |
| Nicotinic symptoms / AChE regeneration | Pralidoxime (2-PAM) → reactivates phosphorylated AChE |
| Note | Time-dependent “aging” of organophosphate-AChE complex requires early 2-PAM administration |
High-Yield Points
- Organophosphates (malathion, parathion, sarin) → irreversible AChE inhibitors → “DUMBBELSS” toxicity
- Atropine does not reverse nicotinic symptoms (muscle weakness, paralysis)
- 2-PAM must be given before aging occurs to regenerate active AChE
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