Patterns of clozapine prescribing in a mental health service in New Zealand

Objective To describe clozapine prescribing in a mental health service in Auckland, New Zealand and compare it with national and international treatment guidelines. Setting A large public mental health service for adults in Auckland, New Zealand. Method A retrospective cross-sectional study of all adult outpatients and stable inpatients being treated with clozapine on 31st March 2007 in one mental health service in Auckland, New Zealand. Data on patient characteristics, diagnosis, duration of illness, number of hospitalisations, legal status relating to their treatment, living situation, marital status and occupational activity were recorded from case notes. Data collected on clozapine included date of initiation, dose and duration of treatment. Prior antipsychotic use and information on all other psychotropic drugs prescribed was also collected. Data were entered into a custom-designed Microsoft Access database and analysed using SPSSv15.0. Main outcome measures Clozapine prescribing patterns and concordance with best practice recommendations for clozapine use. Results 402 adult mental health outpatients and stable inpatients were eligible for inclusion. The mean daily dose of clozapine was 383 (SD 166) mg. For those first presenting after universal government funding, the mean time between presentation and initiation of clozapine, was 2.8 (SD 1.9) years, compared to 5.7 (SD 3.3) years prior to funding. Of those presenting after universal government funding, approximately two-thirds (69.0%) had ≤2 trials with other antipsychotics prior to commencing clozapine; of whom the majority (62.0%) received only second-generation antipsychotics (SGA). Both the number of antipsychotic agents trialled and the time to clozapine initiation has fallen since government subsidy was introduced in 1999. Based on a analysis of annualised hospitalization rates, it appears that shortening the delay to receiving clozapine leads to fewer hospitalisations in this treatment-resistant population, although this did not achieve statistical significance in our study. Conclusions Contemporary management of patients with treatment resistant schizophrenia in New Zealand is broadly in line with national and international best practice guidelines. There is some evidence, based on hospitalisation rates, to support the assertion that shorter delays in accessing clozapine leads to better outcomes. This needs further evaluation using measures of clinical outcome including objective measures of functioning.