Objective Extended release (XR) and immediate release (IR) quetiapine have differing dosing, titration and plasma concentration profiles. The authors assessed whether the use of quetiapine XR and IR in schizophrenia spectrum disorders (SCZ) and bipolar disorder (BD) differ.
Design Retrospective non-interventional registry study.
Setting Secondary healthcare.
Participants All SCZ and BD (ICD-10 codes F20–F29, F30–F31) patients discharged between June 2008 and June 2010 from a Finnish psychiatric hospital with any use of quetiapine during their inpatient stay.
Primary and secondary outcome measures Differences in patient characteristics between quetiapine XR and IR users were tested. To assess the profile of XR versus IR patients, logistic regressions were performed.
Results 43 patients used quetiapine XR, 58 used quetiapine IR and 55 used both formulations (n=156). 102 patients were diagnosed with SCZ and 54 with BD, with no significant differences between the quetiapine formulations. The mean daily dose of quetiapine XR was significantly higher than that of quetiapine IR (542 mg vs 328 mg; p<0.001). This was also true for the SCZ subgroup (XR: 593 mg vs IR: 338 mg; p<0.001) and the BD subgroup (XR: 466 mg vs IR: 308 mg; p=0.009). 48% of all quetiapine IR patients used a mean dose of ≤200 mg compared with 2% of XR patients. Injectable antipsychotics were combined with quetiapine IR but not with quetiapine XR (12% vs 0%; p=0.019). At discharge, quetiapine XR was used as monotherapy to a greater extent than IR (79% vs 44%; p=0.003). The odds for quetiapine XR use in hospital were lower with advancing age, substance abuse diagnosis and prior IR use.
Conclusions Among SCZ and BD inpatients, quetiapine XR was more often used as monotherapy and in significantly higher doses than quetiapine IR. Differential use of the quetiapine formulations appears to depend, at least in part, on patient characteristics.
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To cite: Hallinen T, Soini EJ, Granström O, et al. Differential use of extended and immediate release quetiapine: a retrospective registry study of Finnish inpatients with schizophrenia spectrum and bipolar disorders. BMJ Open 2012;2:e000915. doi:10.1136/bmjopen-2012-000915
Contributors YO, TH, EJS and KH contributed to the study design. TH contributed to data management. TH, EJS and OG designed the statistical analyses which TH carried out. TH and OG drafted the first version of the manuscript. All authors contributed to the interpretation of the results and provided input on drafts of this paper. All authors approved the final version of the manuscript.
Funding This work was funded by AstraZeneca. Employees of Astrazeneca are study authors and as such they contributed to the study design, design and interpretation of data analyses and writing the manuscript.
Competing interests TH and EJS are consultants and shareholders of ESiOR Oy, and EJS is also the CEO of ESiOR Oy, the company commissioned by AstraZeneca to help perform this study. ESiOR Oy also carries out studies, consultancy, education, reporting and health economic evaluations for several pharmaceutical, food industry, diagnostics and device companies, hospitals and academic institutions. OG and YO are employees of AstraZeneca. HJK has received consulting fees from AstraZeneca and payment for lectures from AstraZeneca and GlaxoSmithKline. EL has received consulting fees and payment for lectures from AstraZeneca. EL and HJK are members of AstraZeneca's advisory board for Seroquel. KH declares no conflict of interests.
Ethics approval The ethics approval was provided by the South Karelia Central Hospital Research Ethics Board.
Provenance and peer review Two of the authors (TH and EJS) were commissioned to help perform this study. Externally peer reviewed.
Data sharing statement No additional data are available.
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