What is the recommended work‑up for a suspected quetiapine (Seroquel) overdose?

Quetiapine Overdose Work-Up

Immediate Assessment and Stabilization

Establish and maintain an airway with adequate oxygenation and ventilation as the absolute first priority in quetiapine overdose. 1

• Assess responsiveness and activate emergency response immediately; check breathing and pulse for less than 10 seconds. 2
• Intubate unconscious patients before gastric lavage to prevent aspiration, as obtundation and seizures create significant aspiration risk. 1
• Provide bag-mask ventilation or mechanical ventilation for patients with respiratory depression until spontaneous breathing returns. 3

Cardiovascular Monitoring

Commence continuous electrocardiographic monitoring immediately to detect arrhythmias, as QT prolongation and cardiovascular collapse are the most serious complications. 1

• Monitor for hypotension, sinus tachycardia, and QT prolongation—the hallmark cardiovascular effects of quetiapine toxicity. 1, 4
• Obtain serial ECGs, as tachycardia may persist for 2-3 days and QTc prolongation may last up to 48 hours post-ingestion. 4, 5
• Check for hypokalemia, which has been associated with first-degree heart block in massive overdose. 1

Gastrointestinal Decontamination

Consider gastric lavage (only after intubation if unconscious) followed by activated charcoal with a laxative. 1

• Do not induce emesis due to high risk of aspiration from obtundation, seizures, or dystonic reactions. 1
• Administer activated charcoal early, as absorption appears highly reduced in overdose, either from the overdose itself or charcoal administration. 5

Laboratory and Diagnostic Work-Up

Obtain serum quetiapine concentrations if available, as reported dose correlates highly with peak drug concentration (r²=0.84) and predicts clinical course. 6

• Check electrolytes, particularly potassium, as hypokalemia has been reported with conduction abnormalities. 1
• Be aware that immunoassay tests for tricyclic antidepressants may be falsely positive in quetiapine overdose. 7
• Consider co-ingestion screening, as multiple drug involvement is common and may complicate management. 1

Risk Stratification and Disposition

Admit all patients requiring hospitalization to an intensive care unit, as rapid deterioration in consciousness and hemodynamic instability can occur suddenly. 4

• Patients with reported ingestion <3 grams and Glasgow Coma Scale of 15 at least 4 hours post-ingestion (without co-ingestants) may not require ICU admission or stay >24 hours. 6
• Patients with ingestion ≥3 grams, drowsiness, or co-ingestants require ICU monitoring due to higher risk of intubation, prolonged stay, and cardiovascular complications. 6
• Expect median length of stay of 35 hours for quetiapine overdose patients. 6

Management of Cardiovascular Collapse

Treat hypotension and circulatory collapse with intravenous fluids and sympathomimetic agents, but avoid epinephrine and dopamine as beta-stimulation may worsen hypotension due to quetiapine-induced alpha-blockade. 1

• Consider intravenous lipid emulsion (ILE) for severe cardiovascular collapse refractory to maximum conventional therapy (vasopressors and volume resuscitation), as it may be life-saving. 8
• Extracorporeal circulatory support (ECCS) should be considered for profound cardiovascular depression unresponsive to all other measures. 7

Management of Neurological Complications

Administer anticholinergic medication for severe extrapyramidal symptoms if they occur. 1

• Provide airway protection early for patients with declining consciousness, as rapid progression to coma can occur. 4
• Monitor for seizures, which occur in approximately 11% of cases, particularly with large ingestions (>24 grams). 6

Antiarrhythmic Considerations

Avoid disopyramide, procainamide, and quinidine if antiarrhythmic therapy is needed, as they carry theoretical hazard of additive QT-prolonging effects. 1

• Avoid bretylium due to additive alpha-adrenergic blocking properties that may worsen hypotension. 1

Observation Period

Continue close medical supervision and monitoring until the patient fully recovers, with awareness that the terminal elimination half-life may be 22 hours (not the published 6 hours). 1, 5

• Expect clinical effects and detectable serum concentrations to persist longer than initially anticipated based on the drug's published half-life. 5

Key Pitfalls to Avoid

• Never delay airway management while pursuing other interventions; obtundation can progress rapidly. 4
• Never assume single-drug ingestion; always consider polysubstance overdose. 1
• Never discharge patients early based on initial stability, as deterioration can occur hours after presentation. 4
• Never rely solely on immunoassay drug screens, as false positives for tricyclic antidepressants are common. 7