The pharmacoepidemiology of antipsychotics for adults with schizophrenia in Canada, 2005 to 2009

To describe the frequency and trends in the use of antipsychotics for adults with schizophrenia in Canada from 2005 to 2009.

Analyses were performed on IMS Brogan's Canadian Disease and Therapeutic Index (CDTI). The CDTI is a national physician panel study consisting of a representative sample of physicians both geographically and by specialty. Weighting adjustments are made to estimate national drug recommendations. Quarterly, panel physicians record all therapeutic recommendations during a 2-day period, including patient age, sex, and indication. Antipsychotic recommendations were estimated using CDTI data in which schizophrenia was listed as the indication.

First-generation antipsychotic (FGA) recommendations for adults with schizophrenia increased by 38% between 2005 and 2009, from 329 380 to 454 960 recommendations. There were notable increases in recommendations for chlorpromazine, loxapine, zuclopenthixol, and flupentixol. Second-generation antipsychotic (SGA) recommendations increased to a much lesser extent (9%), which was mostly attributable to an increase in recommendations for clozapine. Drug recommendations for olanzapine decreased by 9%.

The rate of increase of FGA use is now greater than that of SGAs. This may be due to data from recent comparative trials, which suggest that clinical efficacy, and the rate of neurological side effects is similar between FGAs and SGAs. The decreasing use of olanzapine may be due to metabolic adverse effects. The increased use of clozapine may be due to data on its superiority in patients who are treatment resistant.