Overdose Management: Oxcarbazepine, Escitalopram, and Hydroxyzine
Immediate Diagnostic Workup
Order a 12-lead ECG immediately and initiate continuous cardiac monitoring for at least 24 hours due to the significant risk of QRS/QTc prolongation, wide complex tachyarrhythmias, and torsade de pointes from escitalopram and hydroxyzine overdose. 1, 2
Essential Laboratory Tests
Serum sodium level - Critical given oxcarbazepine's propensity to cause severe hyponatremia, which occurs in 2.7-50% of patients and can present with drowsiness, nausea, malaise, diplopia, and altered mental status 3, 4, 5
Basic metabolic panel (BMP) - To assess electrolyte disturbances beyond sodium and evaluate renal function, as renal impairment affects oxcarbazepine pharmacokinetics 6
Renal function tests (creatinine, BUN, creatinine clearance) - Oxcarbazepine elimination is significantly affected by renal impairment 4, 6
Liver function tests - To assess hepatic function, though mild-to-moderate hepatic impairment typically doesn't affect oxcarbazepine metabolism 6
Cardiac Monitoring Requirements
Continuous ECG monitoring for prolonged period - The FDA specifically recommends prolonged cardiac monitoring in escitalopram overdose due to delayed cardiovascular toxicity 1
Serial ECGs - Monitor for QT prolongation and development of arrhythmias, as both escitalopram and hydroxyzine can cause QT prolongation and torsade de pointes 1, 2
Differential Diagnosis
Primary Toxidromes to Consider
Serotonin syndrome - The combination of escitalopram (SSRI) with oxcarbazepine creates risk for this potentially fatal condition, particularly in overdose settings 7
- Look for: altered mental status, autonomic instability, neuromuscular hyperactivity
- This represents the first reported fatality from oxcarbazepine-SSRI interaction 7
CNS depression/sedation - Most common manifestation of hydroxyzine overdose is hypersedation 2
- Oxcarbazepine overdose commonly causes somnolence, drowsiness, depressed level of consciousness, and coma 3, 8
- Escitalopram can cause altered mental status including coma 1
Cardiovascular toxicity - May be delayed in presentation 1
- Hypertension is most common with escitalopram, but hypotension can occur, especially with co-ingestants 1
- Hydroxyzine overdose may require hypotension management with IV fluids and vasopressors (avoid epinephrine as hydroxyzine counteracts its pressor action) 2
Seizures - Can be delayed with escitalopram overdose 1
- Paradoxically, oxcarbazepine overdose can cause convulsions despite being an antiepileptic 3
Hyponatremia-related complications - Particularly relevant with oxcarbazepine at 3x therapeutic dose 4, 5
- Symptoms: nausea, malaise, diplopia, drowsiness, apathy, confusion, potentially seizures
Additional Clinical Presentations
- Anticholinergic effects from hydroxyzine overdose 2
- Tremor, agitation, aggression from oxcarbazepine 3
- Nystagmus, diplopia, dyscoordination, dyskinesia from oxcarbazepine 3
- Nausea and vomiting - common across all three medications 1, 3, 2
Critical Monitoring Parameters
- Vital signs - Frequent monitoring essential, particularly blood pressure and heart rate 2
- Mental status - Serial neurological assessments for progression to coma or seizure activity 1, 3
- Urine output - Decreased output reported in oxcarbazepine overdose 3
- Respiratory status - Dyspnea can occur with oxcarbazepine overdose 3
Common Pitfalls to Avoid
- Delaying cardiac monitoring - Cardiovascular and seizure complications can be delayed, requiring extended observation 1
- Missing hyponatremia - This is often asymptomatic initially but can be severe (as low as 113 mmol/L reported) and dangerous 4
- Using epinephrine for hypotension - Hydroxyzine counteracts epinephrine's pressor action; use levarterenol or metaraminol instead 2
- Assuming single-agent toxicity - The combination creates additive CNS depression and unique risks like serotonin syndrome 7