What is the dosage and administration protocol for atropine?

Atropine Dosage and Administration Protocol

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

Standard Dosing for Bradycardia

Initial dose: 0.5 to 1 mg IV push (without dilution for rapid administration in emergencies) 1, 2, 3

Repeat dosing: Every 3 to 5 minutes if symptomatic bradycardia persists 1

Maximum total dose: 3 mg (or 0.03 to 0.04 mg/kg) 1, 2

Peak effect: Occurs within 3 minutes of IV administration 1, 2

Critical Dosing Warning

Never administer doses below 0.5 mg as this can paradoxically worsen bradycardia through central vagal stimulation, causing further slowing of heart rate and worsening AV conduction. 1, 2 This paradoxical effect is well-documented and represents a common pitfall in atropine administration. 1

Specific Clinical Indications

Class I Indications (Strongly Recommended)

• Symptomatic sinus bradycardia with heart rate <50 bpm associated with hypotension, ischemia, or ventricular arrhythmias 1
• Symptomatic AV block at the AV nodal level (second-degree type I or third-degree with narrow-complex escape rhythm) 1
• Ventricular asystole: 1 mg IV, repeated every 3 to 5 minutes while CPR continues, up to maximum 2.5 mg over 2 hours 1, 2
• Acute inferior MI with symptomatic type I second-degree AV block 1, 2
• Sustained bradycardia and hypotension after nitroglycerin administration 1, 2

Class III (Not Recommended)

• Infranodal AV block (usually associated with anterior MI with wide-complex escape rhythm) - atropine is ineffective and may worsen the block 1
• Asymptomatic sinus bradycardia - treatment not indicated 1
• Bradycardia after heart transplant - atropine can cause paradoxical high-degree AV block in denervated hearts 1

Special Populations

Patients with Coronary Artery Disease

Limit total dose to 0.03 to 0.04 mg/kg to avoid excessive tachycardia that increases myocardial oxygen demand and worsens ischemia. 2, 3 Use the minimum effective dose to achieve a heart rate of approximately 60 bpm rather than aggressively pursuing higher rates. 1

Pediatric Dosing

Initial dose: 0.01 to 0.03 mg/kg IV (range 0.02 mg/kg) 2, 3

Minimum single dose: 0.1 mg (to avoid paradoxical bradycardia) 2

Maximum single dose: 0.5 mg for children, 1.0 mg for adolescents 2

Endotracheal route (when IV unavailable): 0.04 to 0.06 mg/kg (double to triple the IV dose), followed by 5 mL normal saline flush and 5 positive-pressure ventilations 2

Organophosphate/Nerve Agent Poisoning Protocol

This represents a completely different dosing paradigm where standard cardiac dose limits do not apply. 2, 4

Initial dose: 2 to 5 mg IV (not 0.5 mg) 1, 2, 4, 3

Repeat dosing: Double the dose every 20 to 30 minutes until full atropinization is achieved 2, 4

No arbitrary maximum: Cumulative doses may reach 10 to 20 mg in the first 2 to 3 hours, and up to 50 mg in 24 hours 2, 4

Endpoints of Atropinization

• Clear chest on auscultation (resolution of bronchospasm and secretions) 2
• Heart rate >80/min 2
• Systolic blood pressure >80 mm Hg 2
• Drying of secretions 2
• Resolution of miosis (pupil constriction) 2, 4

Critical Pitfall in Toxicological Dosing

Underdosing is more dangerous than overdosing in organophosphate poisoning. 2 Do not confuse standard cardiac dosing (maximum 3 mg) with toxicological dosing (no defined maximum). 2 Titrate aggressively to clinical endpoints, not arbitrary dose limits. 2

Adjunctive Therapy for Organophosphate Poisoning

• Pralidoxime (oxime): 1 to 2 g IV initially, followed by 500 mg/hr continuous infusion 4
• Benzodiazepines: Midazolam or diazepam for seizure control 2, 4
• Early intubation for life-threatening cases 2

Administration Technique

Route: Direct IV bolus (push) without dilution 2, 3

Monitoring: Continuous ECG monitoring during administration to assess heart rate, PR interval, blood pressure, and symptom resolution 2

When Atropine Fails

If full-dose atropine (3 mg total) is ineffective: 1

1. Epinephrine infusion: 2 to 10 mcg/min IV 1
2. Dopamine infusion: 2 to 10 mcg/kg/min IV (or 5 to 20 mcg/kg/min for more severe cases) 1, 2
3. Transcutaneous pacing: Consider when pharmacotherapy fails, though it may not be more effective than second-line drugs 1
4. Theophylline: 100 to 200 mg slow IV injection (maximum 250 mg) for bradycardia after inferior MI, cardiac transplant, or spinal cord injury 1

Adverse Effects to Monitor

• Sinus tachycardia (especially with doses ≥0.8 mg or cumulative doses >2.5 mg) 1, 5
• Ventricular tachycardia or fibrillation (associated with higher initial doses of 1 mg or cumulative doses >2.5 mg) 5
• Increased myocardial ischemia from excessive tachycardia 2, 5
• CNS effects: Hallucinations, fever, toxic psychosis with repeated administration 2, 5
• Anticholinergic symptoms: Dry mouth, blurred vision, photophobia, urinary retention 3

Dose-Related Adverse Effects

Serious adverse effects correlate with either higher initial doses (1.0 mg compared to 0.5 mg) or cumulative doses exceeding 2.5 mg over 2.5 hours. 5 This underscores the importance of titrating to effect rather than administering large boluses. 5

Common Pitfalls to Avoid

1. Administering <0.5 mg doses - causes paradoxical bradycardia 1, 2
2. Using atropine for infranodal (wide-complex) AV block - ineffective and may worsen block 1
3. Administering to heart transplant patients - risk of paradoxical high-degree AV block 1
4. Confusing cardiac dosing with toxicological dosing - organophosphate poisoning requires much higher doses 2
5. Excessive dosing in coronary artery disease - increases ischemia through tachycardia 2, 3
6. Using atropine as sole therapy when transcutaneous pacing is immediately needed - don't delay pacing in unstable patients 2