What is the IM (intramuscular) dose of atropine in a pediatric patient?

IM Atropine Dosing in Pediatric Patients

The intramuscular dose of atropine in pediatric patients is 0.01 mg/kg (10 mcg/kg), not to exceed 0.4 mg per dose, administered subcutaneously or intramuscularly every 4-6 hours for antimuscarinic indications. 1

Standard IM Dosing by Weight

The FDA-approved dosing for intramuscular administration in children is weight-based and indication-specific 1:

Antimuscarinic Indications

• General pediatric dose: 10 mcg/kg (0.01 mg/kg) subcutaneous or IM, maximum 400 mcg (0.4 mg) per dose 1
• Alternative calculation: 300 mcg (0.3 mg) per square meter of body surface area 1
• Frequency: Every 4-6 hours as needed 1

Preanesthesia (Antisialagogue/Antiarrhythmic) - Subcutaneous Dosing

For surgical premedication, weight-stratified dosing is recommended 1:

• Up to 3 kg: 100 mcg (0.1 mg)
• 7-9 kg: 200 mcg (0.2 mg)
• 12-16 kg: 300 mcg (0.3 mg)
• 20-27 kg: 400 mcg (0.4 mg)
• 32 kg: 500 mcg (0.5 mg)
• 41 kg: 600 mcg (0.6 mg)

Emergency/Toxicological Indications (IM Route)

Organophosphate Poisoning

• Initial dose: 0.02-0.05 mg/kg IV preferred, but IM acceptable when IV access unavailable 2
• Maximum single dose: 2-3 mg 2
• Repeat dosing: Every 5-10 minutes until muscarinic symptoms resolve 1
• Pediatric-specific consideration: For nerve agent exposure, start at 0.02 mg/kg, with cumulative doses potentially much higher than standard 2

Critical caveat: In organophosphate poisoning, do not withhold adequate atropine doses due to fear of overdose—inadequate dosing can be fatal 2. Adult patients may require 10-20 mg in the first 2-3 hours, and up to 50 mg in 24 hours 2.

Mushroom Poisoning (Muscarine)

• Dose: 1-2 mg IM or IV every hour until respiratory effects subside 1

Important Clinical Considerations

Route Selection

• IM administration is acceptable when IV/IO access is unavailable or delayed 1
• IV/IO is preferred for acute bradycardia (0.02 mg/kg) and organophosphate poisoning due to faster onset 2, 3
• Endotracheal route can be used as last resort: 0.01-0.03 mg/kg for neonates, 0.03-0.06 mg/kg for older children, followed by saline flush 2

Safety Warnings

• Concentration errors are common: Atropine comes in different concentrations—calculate doses carefully to avoid 10-fold errors 2
• Minimum dose controversy: Recent American Heart Association guidelines (2015) eliminated the 0.1 mg minimum dose requirement for neonates, as 0.02 mg/kg without minimum is effective and safe 3
• Monitor for tachycardia: Excessive heart rate could worsen ischemia in patients with underlying cardiac conditions 2, 3

Common Pitfalls to Avoid

• Do not use IM atropine for acute symptomatic bradycardia when IV/IO access is available—IV route provides faster action 2, 3
• Do not routinely premedicate all pediatric intubations with atropine—it is only indicated for high-risk situations (succinylcholine use, age 28 days to 8 years, septic shock) 4
• Do not use atropine for type II second-degree or third-degree AV block with wide-complex escape rhythm—it is ineffective and potentially harmful 2