Olanzopine overdose

Olanzapine is one of the newer atypical antipsychotic agents which is being increasingly used, as it is effective in the maintenance treatment of chronic schizophrenia. A 33-year-old man was recently admitted to the intensive care unit following an overdose of 30 tablets of olanzapine with an initial Glasgow Coma Scale (GCS) of 15. Over a period of 30–40 min the patient developed continuous vomiting and the GCS deteriorated to 7. Further examination revealed a heart rate of 136 beats. min−1, a respiratory rate of 16 min−1, a blood pressure of 170/110 mmHg and bilaterally constricted pupils. There was no response to a dose of naloxone. Oxygen saturation and arterial blood gases were unremarkable. The patient was intubated and ventilated in view of persistent vomiting and a deteriorating level of consciousness. On arrival at the intensive care unit the patient was stable with normal ECG, clotting screen and creatinine kinase; urine was negative for myoglobin. The patient was ventilated overnight and extubated the following day without complication and made a good recovery. During the admission of this patient, the Poisons Information Centre was contacted for information regarding the potential problems of toxicity with olanzapine. As this agent is relatively new with few reported cases of overdose with which to refer, the effects of toxicity were not clearly defined. The following were suggested as possible toxic effects and are likely to be extrapolated from other similar drugs: CNS depression, convulsions and coma, prolonged QT interval and a-v block, hypotension and the development of neuroleptic malignant syndrome. Of these, the patient had only CNS depression, with hypertension rather than hypotension. Marked vomiting and bilateral pupillary constriction were also a feature. The increasing use of olanzapine in the maintenance treatment of chronic schizophrenia will inevitably result in an increase in the incidence of cases of overdose in this high-risk group of patients. As little is yet known about the effects of this agent in toxic doses, it is important that features of overdose are noted and further cases reported in order to develop a toxicity profile of this drug and to establish the management of overdose.