Emergency Management of Ipratropium Bromide (Atrovent) Mid-Dose Exposure
Ipratropium bromide overdose by inhalation is extremely unlikely to cause systemic toxicity and requires only supportive care, as the drug is poorly absorbed after inhalation even at doses up to four times the recommended amount. 1
Toxicity Profile and Risk Assessment
- Acute systemic overdosage by inhalation is unlikely because ipratropium bromide demonstrates poor systemic absorption after inhalation at up to 4-fold the recommended dose, or after oral administration at up to 40-fold the recommended dose 1
- The oral LD50 in animal studies ranged from 1001-2010 mg/kg in mice, 1667-4000 mg/kg in rats, and 400-1300 mg/kg in dogs, indicating a very high safety margin 1
- Ipratropium is a quaternary ammonium compound that does not cross biological membranes well, limiting systemic anticholinergic effects 2, 3
Clinical Presentation of Overdose
If systemic absorption does occur (typically only with massive oral ingestion), anticholinergic symptoms may include:
- Mydriasis (pupil dilation) 2
- Dryness of mucous membranes 2
- Meteorism with coprostasis (abdominal distension with constipation) 2
- Mild symptoms such as dry mouth, nervousness, dizziness, nausea, or palpitations 3
Emergency Management Protocol
Immediate Assessment
- Evaluate respiratory status including respiratory rate, oxygen saturation, breath sounds, and work of breathing 4, 5
- Assess for paradoxical bronchospasm, which is the primary concern with inhaled ipratropium rather than systemic toxicity 3
- Check vital signs including heart rate and blood pressure 5
Supportive Care
- No specific antidote is required for ipratropium overdose 1
- Provide supplemental oxygen if hypoxemia is present 4, 5
- Monitor for respiratory distress and provide bronchodilators (beta-agonists) if bronchospasm develops 5
- Ensure adequate hydration, as anticholinergic effects can cause drying of respiratory secretions 6
Monitoring Parameters
- Observe for 2-4 hours for development of anticholinergic symptoms 2
- Monitor respiratory function including peak expiratory flow if the patient has underlying obstructive lung disease 4
- Assess for cardiovascular effects, though these are minimal with inhaled ipratropium 7
Key Clinical Considerations
- The primary risk is not from overdose toxicity but from inadequate treatment of the underlying condition (asthma or COPD exacerbation) that prompted ipratropium use 5
- Ipratropium acts primarily on large airways and has minimal systemic absorption when inhaled properly 7
- The drug has a delayed onset of action (within 15 minutes) and duration of 3-5 hours, so effects should resolve spontaneously 3
- Most patients can be safely discharged after a brief observation period if asymptomatic and respiratory status is stable 1, 2
Common Pitfalls to Avoid
- Do not confuse ipratropium overdose with severe asthma or COPD exacerbation requiring aggressive bronchodilator therapy 5
- Avoid unnecessary interventions such as gastric lavage or activated charcoal for inhaled exposures, as systemic absorption is minimal 1
- Do not withhold beta-agonist therapy if bronchospasm is present, as this is the appropriate treatment regardless of ipratropium exposure 5