What is the treatment for a mirtazapine (Remeron) overdose?

Treatment of Mirtazapine (Remeron) Overdose

The management of mirtazapine overdose primarily involves supportive care, as there is no specific antidote for mirtazapine toxicity. Mirtazapine appears to be relatively benign in overdose compared to other antidepressants, with most cases resulting in mild to moderate symptoms that resolve with supportive measures 1.

Initial Assessment and Management

• Establish and maintain an open airway as the first priority, providing bag-mask ventilation for respiratory depression, followed by endotracheal intubation when appropriate 2, 3
• Contact a regional poison center (1-800-222-1222 in the United States) for expert guidance in management 2, 4
• Monitor vital signs, with particular attention to heart rate and blood pressure, as tachycardia and mild hypertension are common 1
• Obtain an ECG to evaluate for possible QT prolongation, which has been reported in serious overdoses 4

Clinical Manifestations of Mirtazapine Overdose

• Common symptoms include drowsiness, sedation, disorientation, impaired memory, and tachycardia 4, 1
• In single-agent overdoses, central nervous system depression is typically mild to moderate (minimum GCS of 10 in reported cases) 1
• Tachycardia occurs in approximately 33% of patients and hypertension in 36% 1
• Serious outcomes including fatalities may occur at dosages higher than recommended doses, especially with mixed overdoses 4

Supportive Care

• Provide respiratory support as needed, which is the cornerstone of management 3
• Consider activated charcoal (50g) if the patient presents within 1-2 hours of ingestion and has an intact airway 5
• Monitor for QT prolongation and Torsades de Pointes, which have been reported in serious overdoses, particularly with mixed ingestions 4
• Provide cardiac monitoring, especially in cases of significant overdose or co-ingestion with other cardiotoxic drugs 1

Special Considerations

• If combined opioid and mirtazapine poisoning is suspected, administer naloxone first before considering other interventions 2, 3
• Be vigilant for co-ingestions, as mixed overdoses (particularly with other CNS depressants) may result in more severe toxicity 2, 6
• Most patients with isolated mirtazapine overdoses can be managed with short-term observation (approximately 6 hours) if they remain stable 5
• Patients who have ingested approximately 10 times the therapeutic dose (therapeutic range 40-80 ng/mL) typically exhibit minimal acute toxicity 5, 2

Common Pitfalls to Avoid

• Failing to recognize mixed overdoses, especially with opioids, benzodiazepines, or alcohol, which can significantly increase toxicity 2, 6
• Administering flumazenil in cases where benzodiazepines may have been co-ingested, as this can precipitate seizures in patients with benzodiazepine dependence 2, 3
• Overlooking the possibility of QT prolongation and Torsades de Pointes, especially in serious or mixed overdoses 4
• Underestimating the need for monitoring in patients with significant co-ingestions, even if mirtazapine alone is relatively safe in overdose 1

Prognosis

• Mirtazapine appears to be relatively safe in overdose compared to other antidepressants, particularly tricyclic antidepressants 7, 8
• In a study of 89 single-agent mirtazapine overdoses, there were no seizures, serotonin toxicity, delirium, arrhythmias, or deaths 1
• The median length of stay for patients with isolated mirtazapine overdose was 14 hours, with no patients requiring intensive care 1