What is the recommended dose of atropine (antimuscarinic agent) per kilogram for a patient bitten by a neurotoxic snake?

Atropine Dosage for Neurotoxic Snake Bite

For neurotoxic snake envenomation, the recommended initial dose of atropine is 0.05 mg/kg IV, which may be doubled and repeated every 10-20 minutes as needed to reverse cholinergic symptoms. 1

Mechanism and Rationale

Neurotoxic snake venom primarily causes paralysis through anticholinesterase effects, leading to:

• Excessive acetylcholine accumulation
• Neuromuscular blockade
• Respiratory compromise
• Bronchorrhea and bronchospasm

Atropine works as a parasympatholytic (anticholinergic) agent that:

• Reduces vagal tone
• Counteracts muscarinic effects of venom
• Helps manage bronchorrhea and bronchospasm
• Does not reverse paralysis (only addresses muscarinic symptoms)

Dosing Protocol

1. Initial dose: 0.05 mg/kg IV 1
2. Subsequent dosing: May double dose and repeat every 10-20 minutes
3. Titration endpoint: Reversal of bronchorrhea, bronchospasm, bradycardia, and hypotension
4. Maximum dosing: Total dose should not exceed 2.5 mg over 2 hours in adults 2

Administration Considerations

• Route: Intravenous (IV) is preferred for rapid action
• Alternative routes: Intramuscular (IM) may be used if IV access unavailable
• Onset of action: Peak effect occurs within 3 minutes of IV administration 2
• Monitoring: Heart rate, blood pressure, respiratory status, and signs of anticholinergic effects

Important Caveats

• Atropine only addresses muscarinic symptoms and will not reverse paralysis or neuromuscular blockade
• The definitive treatment for neurotoxic snake envenomation is antivenom 2
• Atropine should be considered an adjunctive therapy while arranging emergency medical care
• Low doses (<0.5 mg) may paradoxically cause bradycardia 2

Additional Management Considerations

1. Activate emergency services immediately for any venomous snake bite 2
2. Rest and immobilize the bitten extremity 2
3. Remove rings and constricting objects from the affected limb 2
4. Avoid harmful interventions such as:
   • Application of ice
   • Suction or incision
   • Electric shock
   • Tourniquets
   • Pressure immobilization bandaging 2

Pediatric Considerations

For pediatric patients, the dosing remains weight-based at 0.05 mg/kg initially, with careful attention to maximum cumulative dosing. The American Academy of Pediatrics notes that using adult minimum doses can lead to excessive anticholinergic effects in children 1.

Remember that atropine is only part of supportive care while arranging definitive treatment with antivenom, which is the cornerstone of management for neurotoxic snake envenomation.