How the dose is calculated
Atropine is dosed as a single mg/kg amount per administration. Symptomatic bradycardia uses a capped dose; organophosphate poisoning is titrated aggressively against secretions and is not meaningfully capped, since the total dose needed can be very large.
Typical dosing by indication
| Indication | Dose | Frequency | Max |
|---|---|---|---|
| Bradycardia | 0.02 mg/kg | may repeat once at 5 min | 0.5 mg per dose |
| Organophosphate poisoning | 0.02 mg/kg (initial) | repeat q5min, doubling dose | 2 mg (initial dose only) |
For symptomatic bradycardia, a calculated dose below 0.1 mg should still be rounded up to a minimum of 0.1 mg — very small atropine doses can paradoxically worsen bradycardia. For organophosphate poisoning, this calculator's cap applies only to the first dose; the total cumulative dose in severe poisoning is titrated against secretions and pupil size, not capped.
Clinical use
- Atropine is used for symptomatic bradycardia unresponsive to oxygenation/ventilation, and as a key antidote in organophosphate (and some other cholinesterase inhibitor) poisoning.
- In organophosphate poisoning, dosing is titrated against clinical signs — drying secretions, improving heart rate — rather than a fixed calculated ceiling; very large cumulative doses can be needed in severe poisoning.
- A minimum single dose of 0.1 mg is maintained even in very small infants for bradycardia, since doses below this can paradoxically slow the heart rate further via a central vagal effect.
- Not effective for bradycardia caused by high-degree AV block from structural conduction disease — pacing is needed in that setting regardless of atropine dosing.
Frequently asked questions
What is atropine used for?
Atropine treats symptomatic bradycardia (a dangerously slow heart rate) and is a key antidote for organophosphate and related pesticide/nerve agent poisoning.
Why is there a minimum atropine dose for bradycardia?
Very small doses of atropine can paradoxically slow the heart rate further through a central effect, so a minimum single dose of 0.1 mg is maintained even when the calculated weight-based amount is smaller.
Why isn't the organophosphate poisoning dose capped like other drugs?
Severe organophosphate poisoning can require very large cumulative atropine doses to control secretions — dosing is titrated against the patient's clinical response (drying secretions, heart rate) rather than a fixed ceiling.
Does atropine work for all types of bradycardia?
No — it's ineffective for bradycardia caused by high-degree atrioventricular block from structural heart disease, which needs pacing regardless of the atropine dose given.
References
- American Heart Association. Pediatric Advanced Life Support (PALS) Guidelines.
- World Health Organization. Management of Organophosphate Pesticide Poisoning.
- British National Formulary for Children (BNFc) — Atropine.