Prescriptions for antipsychotics in general practice

To the Editor: At the Australasian Schizophrenia Conference in Sydney in October 2002, Professor Patrick McGorry of the Orygen Research Centre, University of Melbourne, presented draft guidelines on the management of schizophrenia and early psychoses.1 One of the recommendations was that atypical antipsychotic drugs should be used as the first-line pharmacological treatment in preference to typical antipsychotics and depot antipsychotics. With a shift in management of schizophrenia to community-based care, the number of patients with schizophrenia managed by general practitioners has increased over the past decade (from 36 per 10 000 encounters in 1990–91 to 45 per 10 000 in 2000–02).2 With the pending introduction of the guidelines, a baseline measure of GP prescribing rates of antipsychotics, both typical and atypical, will allow future measurement of the impact of the guidelines.

We analysed the 1998–2002 data from the Bettering the Evaluation and Care of Health (BEACH) program, a continuous national cross-sectional survey of general practice.3 About 1000 GPs participate in this program every year, each providing details (on structured forms) about 100 consecutive patient encounters. Data collected include GP and patient characteristics, problems managed and treatment provided. We examined 401 300 encounters from 4013 GPs, with 431 537 medications recorded. Prescription rates were calculated and regression analyses performed using SAS software4 to adjust for the cluster effect of the study design.

There were 1988 schizophrenia or psychosis problems managed in the four years of data collection (a rate of 49.5 per 10 000 encounters); 1883 medications were prescribed (94.7 per 100 contacts), of which 926 (49.2%) were typical antipsychotic drugs and 484 (25.7%) were atypical antipsychotic drugs.

In 1998–99, the prescription rate of atypical antipsychotics was 15.7 per 100 contacts with patients with schizophrenia or psychosis (95% CI, 11.8–19.7). This rate increased to 31.1 per 100 contacts (95% CI, 26.3–36.0) in 2001–02. In the same period, the prescription rate for typical antipsychotics fell from 51.3 per 100 contacts (95% CI, 45.6–56.9) in 1998–99 to 40.6 per 100 contacts (95% CI, 35.4–45.8) in 2001–02. Linear regression showed that the prescription rate of atypical antipsychotics had increased by an average of 5.1 per 100 contacts per year over the four years (P < 0.0001), while the prescription rate of typical antipsychotics had decreased by an average of 3.8 per 100 per year (P < 0.005). Over the four-year period, there was no significant increase in the rate of overall prescriptions for people with schizophrenia (92.0 prescriptions per 100 contacts [95% CI, 83.4–100.7] in 1998–99 v 96.3 [95% CI, 89.4–103.3] in 2001–02).

Between 1998 and 2002, the relative prescribing rate of atypical antipsychotics for schizophrenia and other psychoses in general practice nearly doubled. These results show that, even before the introduction of the guidelines, there has been a shift towards prescribing atypical antipsychotics in preference to typical antipsychotics. This change may reflect a change in specialist behaviour, as specialists have a direct effect on GP prescribing.5 The BEACH study will be able to assess the effect of the guidelines on the prescription rate of atypical antipsychotics by GPs.