Loss of consciousness from acute quetiapine overdosage

Background: Quetiapine (Seroquel (R)) is a new atypical antipsychotic agent developed for the treatment of schizophrenia. This dibenzothiazepine derivative possesses high affinity for 5-HT2 receptors with lower affinity for D-1 and D-2 dopamine receptors. In comparison to other antipsychotic agents, quetiapine has less antimuscarinic and alpha(1) antagonist receptor activity. Overdose reports outside of clinical trials are limited. We report an intentional overdose of quetiapine by a schizophrenic. Case Report: A 26-year-old female presented to the emergency department following an alleged ingestion of greater than 10,000 mg of quetiapine. At 1 1/2 hours postingestion, the patient was awake, ambulatory, and responded to verbal stimuli. At 2 1/2 hours postingestion, the patient experienced a decreased level of consciousness and responded only to deep pain. Physical findings included sinus tachycardia, pupils 3-4 mm and sluggish, and BP 135/70. Within 16 hours, the patient became awake and alert and was subsequently extubated. Serum electrolytes and blood count were unremarkable. The electrocardiogram at 18 hours postingestion showed a sinus tachycardia, which lasted for approximately 40 hours postingestion. A follow-up electrocardiogram at 42 hours postingestion was normal. Conclusion: This ingestion resulted in the loss of consciousness with need for airway protection and persistent tachycardia. Major overdoses of quetiapine warrant close observation in an intensive care setting.