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Selective prescribing of atypical antipsychotics§

Authors

  • Nancy S. Breekveldt-Postma PhD,

    Corresponding author
    1. PHARMO Institute, Institute for Pharmacology and Outcomes Research, Utrecht, The Netherlands
    • PHARMO Institute, PO Box 85.222, 3508 AE Utrecht, The Netherlands.
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  • Igor Schillevoort PhD,

    1. Utrecht Institute for Pharmaceutical Sciences, Department of Pharmacoepidemiology and Pharmacotherapy, Utrecht University, Utrecht, The Netherlands
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  • Willem A. Nolen MD, PhD,

    1. Department of Psychiatry, University Medical Centre Utrecht and Altrecht Institute for Mental Health Care, Utrecht, The Netherlands
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  • Christiaan P. W. M. Veraart MSc,

    1. Eli Lilly Nederland bv, Nieuwegein, The Netherlands
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  • Ron M. C. Herings PhD

    1. PHARMO Institute, Institute for Pharmacology and Outcomes Research, Utrecht, The Netherlands
    2. Utrecht Institute for Pharmaceutical Sciences, Department of Pharmacoepidemiology and Pharmacotherapy, Utrecht University, Utrecht, The Netherlands
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  • No conflict of interest was declared.

  • W.A. Nolen has been paid as a consultant (or in a similar capacity) by a company with a vested interest in the product being studied, on issues unrelated to the product being studied.

  • §

    C.P.W.M. Veraart is an employee of the company whose product is being studied.

Abstract

Purpose

The aim of the study was to investigate whether the most recent introduced atypical antipsychotics olanzapine and risperidone were preferentially prescribed to patients susceptible to develop extrapyramidal side effects (EPS) and those not responding adequately to typical antipsychotics.

Methods

Data were obtained from the Dutch PHARMO system that includes complete medication and hospital admission records of 675 000 residents of 14 Dutch cities. A total number of 129 new users of olanzapine and 142 new users of risperidone as well as 507 new users of typical antipsychotic drugs were identified from our database in the period of 1996–1998. The prevalence of markers of EPS, therapy resistance and therapy non-compliance were assessed in the period of 1 year prior to a new start of an antipsychotic.

Results

New use of olanzapine and risperidone was significantly associated with previous use of other antipsychotics (odds ratio 4.0, 95%CI: 2.5–6.7 and odds ratio 3.0, 95%CI: 2.0–4.7, respectively). New use of olanzapine and risperidone was also associated with previous use of anticholinergic drugs compared to users of typical antipsychotics (over three and two times more, respectively). This effect diminished when adjusted for previous use of antipsychotics.

Conclusions

In particular olanzapine and also risperidone were selectively prescribed to patients formerly treated with other antipsychotics and to those susceptible for EPS. If not recognised or controlled for, observational studies comparing different antipsychotic drugs may produce biased results on efficacy or frequency of side effects for the different types of antipsychotics. Copyright © 2004 John Wiley & Sons, Ltd.

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