What is the management for an olanzapine (atypical antipsychotic) overdose?

Management of Olanzapine Overdose

Activated charcoal administration is the first-line treatment for olanzapine overdose if the patient presents within 1-2 hours of ingestion, followed by supportive care with close monitoring for fluctuating mental status, anticholinergic effects, and cardiorespiratory complications. 1, 2

Initial Assessment and Stabilization

• Assess and secure airway, breathing, and circulation
• Obtain vital signs, including temperature (monitor for hyperthermia)
• Perform neurological assessment, noting level of consciousness and pupil size
• Obtain ECG to assess for QT prolongation or arrhythmias
• Check blood glucose (olanzapine overdose can cause hyperglycemia)
• Consider laboratory tests: electrolytes, renal function, CPK (risk of rhabdomyolysis)

Decontamination and Specific Treatments

1. Activated charcoal:

   • Administer 1g/kg if presentation is within 1-2 hours of ingestion 1
   • Reduces olanzapine absorption by approximately 60%
   • Contraindicated if airway is not protected or risk of aspiration

2. Physostigmine (for severe anticholinergic toxicity):

   • Consider in cases of significant anticholinergic delirium or agitation
   • Dosing: 0.5-2 mg IV, may repeat if needed 3, 4
   • Use with caution and only when benefits outweigh risks
   • Contraindicated in patients with cardiovascular disease or asthma

Monitoring and Supportive Care

• Continuous cardiac monitoring for at least 24 hours
• Frequent neurological assessments (every 1-2 hours)
• Monitor for fluctuating mental status - characteristic finding in moderate to high olanzapine overdoses 2
• Blood glucose monitoring - hyperglycemia may require insulin therapy 5
• Temperature monitoring - treat hyperthermia if present
• Fluid management - maintain adequate hydration

Management of Specific Complications

1. CNS Depression/Agitation:

   • Expect unpredictable fluctuations between somnolence/coma and agitation/aggression 2, 6
   • Provide supportive care and safe environment
   • Avoid benzodiazepines if possible due to risk of respiratory depression 7
   • Physical restraints may be necessary in severe agitation cases 6

2. Anticholinergic Effects:

   • Miosis is paradoxically common (31% of cases) despite anticholinergic properties 2
   • Monitor for dry mucous membranes, decreased bowel sounds, urinary retention
   • Provide supportive care (e.g., bladder catheterization if needed)

3. Cardiovascular Effects:

   • Treat tachycardia with supportive measures
   • Monitor for orthostatic hypotension, especially if co-ingestion with benzodiazepines 1
   • Avoid medications that may prolong QT interval

4. Metabolic Effects:

   • Treat hyperglycemia with insulin if needed 5
   • Monitor for metabolic acidosis

Disposition and Prognosis

• Patients with moderate to severe symptoms (doses >120 mg) should be admitted for observation 2
• Observation period of at least 6 hours is recommended for all patients 6
• Most patients recover within 48 hours even with significant overdoses 2
• ICU admission is indicated for patients with:
  • GCS <9
  • Respiratory depression requiring ventilatory support
  • Severe agitation/delirium requiring chemical or physical restraint
  • Significant cardiac abnormalities

Special Considerations

• Co-ingestions: Particularly dangerous with benzodiazepines or alcohol due to increased risk of respiratory depression 7, 1
• Chronic olanzapine users: May have less severe symptoms compared to naïve users 6
• Elderly patients: More sensitive to anticholinergic effects and CNS depression 7

Common Pitfalls to Avoid

• Failing to anticipate fluctuating mental status, leading to premature discharge
• Underestimating the need for extended monitoring (at least 6 hours)
• Overlooking hyperglycemia, which may require insulin therapy
• Using benzodiazepines for agitation, which may worsen respiratory depression
• Discharging patients too early (symptoms can persist for up to 48 hours)

The management of olanzapine overdose requires vigilant monitoring and supportive care, with particular attention to the characteristic fluctuating mental status and potential metabolic complications.