Olanzapine Overdose Cause of Acute Extrapyramidal Symptoms

Quentin, a 9-year-old boy who weighed 64 lb and had no prior exposure to psychotropic medication, took 100 mg of his mother"s olanzapine and an indeterminate amount of acetominophen in an apparent suicide attempt. At presentation in the emergency department about 2 hours after ingestion, Quentin was combative and unable to follow commands. He also had tachycardia, hypotension, and decreased gastrointestinal motility. He was treated with elective intubation for airway management and with intravenous fluids and norepinephrine for pressure support. Activated charcoal and n-acetyl cysteine were used to prevent further drug toxicity. Cisapride, ondansetron, and metoclopramide were given for promotility effects. Significant laboratory abnormalities during his hospitalization included peak levels of the following: acetaminophen (158 mg/ml), aspartate aminotransferase (93 U/liter), alanine aminotransferase (47 U/liter), and lactate dehydrogenase (434 U/liter). Quentin’s platelets were elevated (502,000/mm³). Quentin did well with treatment and was extubated within 15 hours of admission. By about 36 hours after ingestion and after resolution of his presenting symptoms Quentin developed “jitteriness” and hyperreflexia followed by tremors of the extremities, cogwheel rigidity, a stiff jaw, oculogyric signs, and severe dystonia of the neck. These symptoms were treated with intravenous diphenhydramine for 24 hours and then with oral diphenhydramine for 9 days thereafter. During the course of this treatment, his extrapyramidal symptoms improved significantly. At 13 days after ingestion, Quentin had only a slight upper extremity tremor and no subjective complaints.