title: Dropout rates with olanzapine or risperidone: a multi-centre observational study.
abstract: OBJECTIVE
  In patients with schizophrenia, risperidone and olanzapine are the two most commonly used atypical anti-psychotics. A recent meta-analysis based on randomized trials suggests that, in the long term, olanzapine can have a lower frequency of treatment discontinuation (or dropout) in comparison with risperidone. To better test this hypothesis, our observational study was aimed at assessing whether or not this advantage of olanzapine versus risperidone could be confirmed in a patient series examined in an observational setting.
  
  
  METHODS
  Our study was based on a retrospective multi-centre observational design. We collected the following information from each patient: demographic characteristics; current anti-psychotic treatment (olanzapine or risperidone, under the condition of a stable therapy over months -1 to -4); cumulative dose of the drug; previous anti-psychotic treatment (during months -5, -6, -7 and/or, when available, also before month -7); daily dose and treatment duration. Our primary analysis traced back the patient's history from the date of enrollment retrospectively up to month -7. The secondary analysis followed-up the patient's history prior to month -7, thus extending this retrospective recording as long as possible (depending on what information was actually available for individual patients).
  
  
  RESULTS
  The patients were enrolled from 31 institutions. In our primary analysis (months -1 to -7), a total of 144 patients were included; in this subgroup treated with olanzapine or risperidone as initial drug ( n=94), we observed 4 of 54 switches from olanzapine to risperidone and 11 of 40 switches from risperidone to olanzapine ( P=0.01). A total of 454 patients were enrolled in our secondary analysis (from month -1 up to month -73); the same comparison showed 9 of 236 switches from olanzapine to risperidone and 17 of 150 switches from risperidone to olanzapine ( P=0.004).
  
  
  CONCLUSIONS
  Our analysis confirms the results of a recent meta-analysis and shows that olanzapine might imply a lower risk of dropout than risperidone.
authors.affiliation: Laboratorio SIFO di Farmacoeconomia, Drug Information Centre, Azienda Ospedaliera Careggi, viale Morgagni 85, 50134 Florence, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Pelagotti
authors.forename: B
authors.initials: B
authors.lastname: Santarlasci
authors.forename: F
authors.initials: F
authors.lastname: Vacca
authors.forename: S
authors.initials: S
authors.lastname: Trippoli
authors.forename: A
authors.initials: A
authors.lastname: Messori
mesh_terms: D000328:Adult; D014150:Antipsychotic Agents / Q000627:therapeutic use*; D001569:Benzodiazepines / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D008297:Male; D015201:Meta-Analysis as Topic; D015337:Multicenter Studies as Topic; D000077152:Olanzapine; D010352:Patient Dropouts / Q000706:statistics & numerical data*; D017891:Pharmacoepidemiology; D011618:Psychotic Disorders / Q000188:drug therapy*; D012189:Retrospective Studies; D018967:Risperidone / Q000627:therapeutic use*
chemical_list: D014150:Antipsychotic Agents; D001569:Benzodiazepines; D018967:Risperidone; D000077152:Olanzapine