Effect of switching antipsychotics on antiparkinsonian medication use in schizophrenia: a population-based study

Background: The extent to which atypical antipsychotics have a lower incidence of extrapyramidal symptoms than typical antipsychotics has not been well-evaluated in community practice. Aims: To examine the effects of switching antipsychotics on antiparkinsonian medication use among individuals with schizophrenia in UK general practices. Method: We included those switched from typical to atypical antipsychotics (n=209) or from one typical antipsychotic to another (n=261) from 1994 to 1998. Results: Antiparkinsonian drug prescribing dropped by 9.2% after switching to atypical antipsychotics (P<0.0001). Switching to olanzapine decreased the rate by 19.2% (P<0.0001), but switching to risperidone had no impact. After switching from one typical antipsychotic to another, antiparkinsonian drug prescribing increased by 12.9% (P<0.0001). Conclusions: Reduction in antiparkinsonian medication use after switching to atypical antipsychotics was substantial in community practice but not as large as in randomised controlled trials. The rate of reduction varied according to the type of medication.