A 28-year-old woman is brought to the emergency department 2 hours after ingesting an unknown number of organophosphate pesticide tablets during a suicide attempt. She presents with excessive salivation, miosis, muscle fasciculations, and respiratory distress. Which is the drug of choice for immediate management of organophosphate poisoning?

Explanation

## Management of Organophosphate Poisoning **Key Point:** Atropine is the first-line and most critical drug in organophosphate poisoning because it rapidly reverses the life-threatening muscarinic manifestations (excessive salivation, bronchospasm, bradycardia, miosis). ### Mechanism of Organophosphate Toxicity Organophosphates irreversibly inhibit acetylcholinesterase, leading to accumulation of acetylcholine at both nicotinic and muscarinic receptors. ### Role of Atropine - **Muscarinic antagonist** — blocks excessive cholinergic effects at muscarinic receptors - Relieves bronchospasm, excessive salivation, bradycardia, and miosis - Given in **large, repeated doses** (2–5 mg IV initially, then every 5–10 minutes until signs of atropinization appear) - Does **NOT** reverse nicotinic effects (muscle fasciculations, weakness, paralysis) ### Complementary Role of Pralidoxime - **Oxime** that reactivates acetylcholinesterase by removing the phosphoryl group - Effective only if given **early** (within 24–48 hours, ideally within first 6 hours) - Reverses **both muscarinic and nicotinic** effects - Given after atropine, not instead of it - Dose: 1–2 g IV over 15–30 minutes, then 500 mg–1 g IV every 4–6 hours ### Treatment Algorithm ```mermaid flowchart TD A[Organophosphate Poisoning]:::outcome --> B[Immediate: Atropine IV]:::action B --> C{Life-threatening muscarinic effects controlled?}:::decision C -->|No| D[Repeat atropine every 5-10 min]:::action C -->|Yes| E[Add Pralidoxime]:::action E --> F[Supportive care: airway, ventilation]:::action F --> G[Monitor for recurrence]:::outcome ``` **High-Yield:** Atropine is given **first and repeatedly** until atropinization (dry mouth, dilated pupils, tachycardia). Pralidoxime is added **after** atropine, not as a replacement. **Clinical Pearl:** The combination of atropine + pralidoxime is synergistic. Atropine buys time while pralidoxime regenerates the enzyme. [cite:KD Tripathi 8e Ch 11]