Delirium during clozapine treatment: incidence and associated risk factors.

ABSTRACT

BACKGROUND: Incidence and risk factors for delirium during clozapine treatment require further clarification. METHODS: We used computerized pharmacy records to identify all adult psychiatric inpatients treated with clozapine (1995-96), reviewed their medical records to score incidence and severity of delirium, and tested associations with potential risk factors. RESULTS: Subjects (n = 139) were 72 women and 67 men, aged 40.8 +/- 12.1 years, hospitalized for 24.9 +/- 23.3 days, and given clozapine, gradually increased to an average daily dose of 282 +/- 203 mg (3.45 +/- 2.45 mg/kg) for 18.9 +/- 16.4 days. Delirium was diagnosed in 14 (10.1 % incidence, or 1.48 cases/person-years of exposure); 71.4 % of cases were moderate or severe. Associated factors were co-treatment with other centrally antimuscarinic agents, poor clinical outcome, older age, and longer hospitalization (by 17.5 days, increasing cost); sex, diagnosis or medical co-morbidity, and daily clozapine dose, which fell with age, were unrelated. CONCLUSIONS: Delirium was found in 10 % of clozapine-treated inpatients, particularly in older patients exposed to other central anticholinergics. Delirium was inconsistently recognized clinically in milder cases and was associated with increased length-of-stay and higher costs, and inferior clinical outcome.