What is the recommended dosage of atropine for adult and pediatric patients with various indications, including bradycardia and organophosphate poisoning?

Atropine Dosage Guidelines

Bradycardia in Adults

For symptomatic bradycardia, administer atropine 0.5 mg IV bolus every 3-5 minutes up to a maximum total dose of 3 mg. 1

• The initial dose must be at least 0.5 mg to avoid paradoxical bradycardia caused by central vagal stimulation that occurs with lower doses 2, 1
• Repeat 0.5 mg doses every 5 minutes as needed until symptoms resolve 3
• Peak action occurs within 3 minutes of IV administration 3
• In patients with coronary artery disease, limit total cumulative dose to 0.03-0.04 mg/kg to prevent increased myocardial oxygen demand and worsening ischemia 1, 4

Specific Indications for Bradycardia (Class I)

• Sinus bradycardia with low cardiac output, peripheral hypoperfusion, or frequent premature ventricular contractions 3
• Acute inferior MI with symptomatic type I second-degree AV block 3
• Bradycardia and hypotension following nitroglycerin administration 3

Critical Pitfall: Heart Transplant Patients

• Do not use atropine in heart transplant patients without evidence of autonomic reinnervation, as it causes paradoxical cardiac block or sinus arrest in approximately 20% of these patients 2

Organophosphate/Carbamate Poisoning in Adults

For severe organophosphate or carbamate poisoning with bronchospasm, bronchorrhea, seizures, or significant bradycardia, give an initial dose of 2-5 mg IV, then double the dose every 20-30 minutes until full atropinization is achieved. 3, 5, 1

• Full atropinization endpoints: clear chest on auscultation, heart rate >80/min, systolic blood pressure >80 mm Hg, and drying of secretions 3
• There is no arbitrary maximum dose in organophosphate poisoning—cumulative doses may reach 10-20 mg in the first 2-3 hours and up to 50 mg in 24 hours 1
• Maintenance atropinization can be achieved with continuous IV infusion after initial boluses 3
• Underdosing is more dangerous than overdosing in this context—titrate aggressively to reverse bronchospasm and dry secretions 1

Adjunctive Therapy for Organophosphate Poisoning

• Pralidoxime (2-PAM): 1-2 g IV initially, followed by 500 mg/hour continuous infusion 5
• Benzodiazepines (diazepam first-line or midazolam) for seizure control and agitation 3, 5
• Early endotracheal intubation for life-threatening poisoning 3

Pediatric Dosing

For standard indications (bradycardia), give 0.02 mg/kg IV (range 0.01-0.03 mg/kg) with a minimum single dose of 0.1 mg and maximum single dose of 0.5 mg. 1

• Maximum total dose for children: 1 mg 1
• Maximum total dose for adolescents: 2 mg 1

For organophosphate poisoning in children, give 0.05 mg/kg IV (up to adult dose of 2-5 mg), then double as needed without a defined maximum, titrated to clinical effect. 5, 1

Alternative Route When IV Access Unavailable

• Endotracheal administration: 0.04-0.06 mg/kg (double to triple the IV dose), followed by 5 mL normal saline flush and 5 consecutive positive-pressure ventilations 1

Cardiac Arrest (Asystole)

For ventricular asystole, give 1 mg IV, repeated every 3-5 minutes if asystole persists while CPR continues, up to a maximum cumulative dose of 2.5 mg over 2.5 hours. 3

Administration Technique

• Administer as direct IV bolus (push) without dilution for rapid administration in emergencies 1
• Continuous ECG monitoring is mandatory during administration 1

When Atropine Fails or Is Contraindicated

If bradycardia persists despite adequate atropine dosing:

• Epinephrine infusion: 2-10 mcg/min IV 2, 1
• Dopamine infusion: 5-20 mcg/kg/min IV 2, 1
• Transcutaneous pacing for unstable patients with poor perfusion 1

Critical Warnings and Adverse Effects

• Doses <0.5 mg or non-IV routes may cause paradoxical bradycardia and worsened AV conduction 3, 2
• Repeated administration may cause CNS effects including hallucinations, fever, and toxic psychosis 3, 6
• Serious adverse effects (ventricular tachycardia/fibrillation, sustained sinus tachycardia) correlate with initial doses ≥1.0 mg or cumulative doses exceeding 2.5 mg over 2.5 hours in cardiac patients 6
• Sinus tachycardia following atropine may increase myocardial ischemia 3