Ambulatory use of olanzapine and risperidone: a population-based study on persistence and the use of concomitant therapy in the treatment of schizophrenia.
OBJECTIVE
To assess treatment discontinuation and concomitant use of other antipsychotics among individuals initiated on olanzapine or risperidone for the treatment of schizophrenia.


METHODS
Using data from the Quebec health insurance plan and the Quebec database for hospitalization, we conducted a population-based cohort study of patients for whom a first claim for olanzapine or risperidone was submitted between 1 January 1997 and 31 August 1999. Included were 6405 patients with schizophrenia whom we followed from the date of the first claim for olanzapine or risperidone either to discontinuation date, end of eligibility for the drug plan, 365 days, date of moving out of the province, or date of death. We used Cox regression models to compute hazards ratios (HRs) of having the treatment discontinued and logistic regression models to compute odds ratios (ORs) among persisting patients of having any concomitant antipsychotic prescription. All models were adjusted for age, sex, schizophrenia disorder, comorbidity, region, beneficiary type, substance use disorder, and prior hospitalization for mental illness.


RESULTS
Compared with risperidone users (n = 2718), discontinuation rates were lower for olanzapine users (n = 3687; HR = 0.79; 95%CI, 0.74 to 0.84). The odds of receiving any concomitant antipsychotic prescription did not differ statistically between olanzapine and risperidone users (OR 0.85; 95%CI, 0.71 to 1.01).


CONCLUSIONS
The study results suggest that new users of olanzapine were less likely to discontinue their initial treatment than were new users of risperidone, although discontinuation was high in both groups. Among those who persisted, concomitant use of other antipsychotics did not differ between olanzapine users and risperidone users.
Faculté de pharmacie, Université Laval, Quebec City, Quebec.
Dan
D
Cooper
Jocelyne
J
Moisan
Michel
M
Gaudet
Belkacem
B
Abdous
Jean-Pierre
JP
Grégoire
D000328:Adult; D000368:Aged; D000553:Ambulatory Care; D014150:Antipsychotic Agents / Q000627:therapeutic use*; D001569:Benzodiazepines / Q000627:therapeutic use; D003024:Clozapine / Q000627:therapeutic use; D015331:Cohort Studies; D003987:Dibenzothiazepines / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D000077152:Olanzapine; D011159:Population Surveillance; D000069348:Quetiapine Fumarate; D016032:Randomized Controlled Trials as Topic; D018967:Risperidone / Q000627:therapeutic use*; D012559:Schizophrenia / Q000188:drug therapy*; D013997:Time Factors
D014150:Antipsychotic Agents; D003987:Dibenzothiazepines; D001569:Benzodiazepines; D000069348:Quetiapine Fumarate; D003024:Clozapine; D018967:Risperidone; D000077152:Olanzapine