An audit of outpatient antipsychotic usage in the three health sectors of Auckland, New Zealand

Objective: To examine antipsychotic usage in outpatients in three community mental health centres. Method: A retrospective chart review was conducted for all outpatient files that were active in March 2000 at all community mental health services in Auckland (population 1.3 million). All patients prescribed an antipsychotic had information entered into a specifically designed computer software program. The antipsychotic, dose and route of administration were recorded. The diagnosis, number of hospitalizations, ethnicity and gender were also collected. Results: 6558 community files were audited and 3254 people were prescribed antipsychotics; 3178 (97.6%) files had adequate information for study inclusion. The mean antipsychotic daily dose in chlorpromazine equivalents (CPZe) was 360 mg. Most of the population (76.6%) was prescribed an oral antipsychotic alone, 14.9% were prescribed depot antipsychotic only and 8.4% were on a depot and oral antipsychotic. The average daily dose prescribed for people on antipsychotic polypharmacy was 601 mg CPZe compared with 312 mg CPZe for those on a single antipsychotic. There were 2300 patients with schizophrenia (72.5% of cohort) and 585 patients with bipolar affective disorder (18.5%). The mean total daily dose in CPZe was significantly higher for schizophrenia than any other psychotic diagnoses. Regional analysis showed differences in the doses and type of antipsychotics prescribed; one health sector had significantly higher daily doses while another was significantly more likely to prescribe atypical antipsychotics and correspondingly fewer depot antipsychotics. Conclusions: There is a significant variation in the prescribing of antipsychotics across the three Auckland health sectors. The variation relates to dosage used, type of antipsychotics prescribed and effect of multiple antipsychotic prescribing. Combination therapy of more than one oral antipsychotic or a combination of oral and depot antipsychotics leads to a significant trend of higher doses in excess of best practice guidelines.