Does of atropine in op poisoning
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Searching for atropine dosing in organophosphate poisoning.
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atropine dose organophosphate poisoning management
Harrison's Principles of Internal Medicine, Twenty First Edition
Page 13075
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organophosphate poisoning clinical features cholinergic toxidrome treatment
Harrison's Principles of Internal Medicine, Twenty First Edition
Page 13012
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Atropine in Organophosphate (OP) Poisoning
Why Atropine?
Organophosphates inhibit acetylcholinesterase, causing accumulation of acetylcholine at muscarinic and nicotinic receptors. Atropine is a competitive muscarinic antagonist — it blocks the excess acetylcholine at muscarinic receptors, reversing the life-threatening effects.
Atropine does NOT reverse nicotinic effects (muscle weakness, paralysis) — oximes (pralidoxime) are needed for that.
Dosing Protocol
Initial (Test) Dose
| Severity | Initial IV Dose |
|---|---|
| Mild–Moderate | 1–2 mg IV |
| Severe (unconscious, seizures, severe bronchospasm) | 2–4 mg IV (some protocols start at 5 mg) |
Repeat Dosing — "Atropinization"
- Double the dose every 5–10 minutes until the end-point of atropinization is achieved.
- In severe cases, total doses of 20–100 mg or more over the first few hours are commonly required.
- Some patients have required >1000 mg in the first 24 hours.
End-Point: "Atropinization" (NOT pupil dilation)
Adequate atropinization is defined by:
- ✅ Dry secretions (no bronchorrhea, no oral/tracheal secretions)
- ✅ Clear chest (no wheeze/crackles — bronchospasm resolved)
- ✅ Heart rate > 80 bpm
- ✅ Systolic BP > 80 mmHg
Pupil dilation and dry skin are NOT reliable endpoints — do not use them to guide dosing.
Maintenance Infusion
Once atropinized:
- Start an IV infusion at 10–20% of the total loading dose per hour
- Titrate down based on clinical response
- Taper gradually over 12–24 hours once stable
Route of Administration
| Situation | Route |
|---|---|
| Stable IV access | IV bolus (preferred) |
| No IV access | IM (auto-injector or standard syringe) |
| Endotracheal (rare, if intubated and no IV) | 2–3× IV dose diluted in saline |
Severity-Based Summary
| Severity | Features | Atropine Starting Dose |
|---|---|---|
| Mild | Miosis, excess secretions, nausea | 1–2 mg IV, repeat q10 min |
| Moderate | Bronchospasm, bradycardia, confusion | 2–4 mg IV, repeat q5 min |
| Severe | Coma, seizures, apnea, severe bronchorrhea | 4–5 mg IV bolus, double q5 min |
Adjunct: Oximes (Pralidoxime / 2-PAM)
- Reactivates acetylcholinesterase if given before "aging" (irreversible binding)
- Dose: 1–2 g IV over 15–30 min, then infusion at 200–400 mg/hr
- Must be given early (within hours of exposure; less effective after 24–48 hours)
- Effective for nicotinic effects (muscle weakness, paralysis)
Key Points to Remember
- There is no upper limit for atropine in OP poisoning — titrate to clinical response, not a fixed total dose.
- The goal is dry lungs, not dry skin or dilated pupils.
- Hypoxia must be corrected before atropine to avoid precipitating ventricular fibrillation.
- Benzodiazepines are the drug of choice for OP-induced seizures.
- Glycopyrrolate (0.2 mg IV) can be used as an alternative if tachycardia limits atropine.
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