Abstract
We report a 32-year-old male treated for bipolar disorder with quetiapine and lithium, who presented with an impulsive overdose of 15 g of quetiapine. He was found unconscious with a Glasgow Coma Scale, GCS 6, hypothermic and incontinent in his home 48 h after ingestion. It was presumed he had a fall post-overdose due to postural hypotension that resulted in head injury. A CT scan showed subgaleal haematoma, other injuries include shoulder dislocation and multiple bruising. Serial electrocardiogram (ECG) showed sinus tachycardia, but nil QTc prolongation. Routine bloods showed low potassium which was treated with intravenous (IV) replacement. Interestingly, Creatine Kinase at admission was 6953 (baseline, day 3 of overdose), that peaked to 13610 on day 4. The CK levels then gradually reduced to 8752 (day 5) and became normal on day 10. The white cell count (19∗10∗9) and C-reactive protein (CRP) levels were elevated. Thyroid, kidney, liver functions and lithium levels remained normal.
The patient was admitted to the intensive care unit (ICU) for management with IV fluids, electrolyte replacement, warming and monitoring. He remained in ICU for 3 days where GCS slowly improved and agitation was managed with light sedation. The patient recovered from the medical effects and later was treated in a psychiatric setting over four weeks with lithium and duloxetine. Additional investigation with MRI brain, cerebral perfusion scan and a detailed neuropsychological assessment ruled out subtle brain damage that could have been sustained from hypoxic brain injury.
The published literature on the clinical manifestations of quetiapine overdose includes sedation, hypotension respiratory depression, hypokalemia, seizures, delirium, and agitation. Sinus tachycardia was often documented, however rarely malignant and not always associated with QTc prolongation [1,2]. Supportive and symptomatic management in the intensive care unit with mechanical ventilation is frequently required and most patients recover. The mortality rate is low though still reported [3,4,5].
The key features of the case were the unexplained elevated CK and hypothermia. The cause of elevated CK levels could be attributed to muscle damage sustained by the fall with increased inflammatory markers CRP and WBC count. However, muscle damage alone cannot explain the degree of CK elevation (above 10000). Sinus tachycardia with rapid rise and spontaneous resolution of CK within a week treated in an antipsychotic-free environment warrants a diagnosis of neuroleptic malignant syndrome (NMS). However, other features of NMS, muscular rigidity, autonomic dysfunction, hyperpyrexia (patient was hypothermic) were absent.
Quetiapine is marketed as a safe antipsychotic medication with a low risk of NMS and extrapyramidal reactions. As the indications for quetiapine use widens to include anxiety and personality disorders, there is a potential for an increase in the number of overdoses seen.