A 29-year-old male of Yemeni descent detained in a medium secure unit was commenced on clozapine; after 4 weeks of treatment he was taking a total of 275 mg in divided doses. He developed nausea and vomiting which progressed over 36 hours to a point where he needed to be urgently transferred to the local accident and emergency unit. At assessment he was experiencing breathing problems, vomiting and he was incontinent of urine; he had a Glasgow Coma Scale score of five. He was immediately transferred to the intensive care unit. The differential diagnoses included drug overdose, alcohol intoxication and clozapine-induced hyperglycaemia. His blood chemistry showed evidence of diabetic ketoacidosis; his blood glucose level was grossly elevated. The clozapine was stopped and the patient was given appropriate treatment with glycaemic agents.
In summary, the patient had become seriously unwell over a period of 36 hours. Apart from having a slightly raised body mass index, he was fit and well and had no family history of diabetes. His pre-treatment blood glucose had been normal.
Diabetic ketoacidosis is over ten times more common in patients treated with atypical antipsychotics than in the general population, Reference Akintomide, Williams Porter and Pierce1 although the evidence is largely restricted to case reports and series. Reference Adshead and du Feu2 Clozapine has a higher risk of ketoacidosis than other oral antipsychotics Reference Munoz-Baell and Ruiz3 and it tends to develop after a shorter duration of treatment, with a high proportion of patients developing it within 3-6 months. Low doses, being a young male and having a negative family history seem to be significant risk factors. Reference Ralston, Zazove and Gorenflo4 There is also significant mortality. 5 The unusual aspect of this case (although not unknown) was the occurrence of diabetic ketoacidosis during the titration phase of treatment.
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