Atropine dosing for organophosphate poisoning in ALS: which is correct?

• A. Atropine, 2 mg IV/IO, repeat at 2 mg increments every five minutes if patient remains symptomatic.
• B. Atropine, 1 mg IV/IO, repeat every five minutes up to 3 mg
• C. Atropine, 4 mg IV/IO, once
• D. Atropine, 0.5 mg IV/IO every 2 minutes

Answer: (A)

Organophosphate poisoning causes a surge of acetylcholine at muscarinic receptors, leading to excessive secretions, bronchospasm, bronchorrhea, miosis, and bradycardia. Atropine works by blocking those muscarinic receptors, but it must be given in titrating doses so you achieve enough anticholinergic effect without overshooting.

The best approach is to start with a 2 mg IV/IO dose and repeat every 5 minutes in 2 mg increments, continuing until there is clear improvement in airway and secretions (adequate atropinization). This titration captures rapid changes in the patient and ensures you’re providing enough drug to counteract the muscarinic effects. Using a smaller initial dose or fixed high-dose strategies without titration risks under-treatment or unnecessary anticholinergic toxicity, and very rapid small doses don’t give a meaningful assessment of response.