Characteristics of bipolar disorder patients treated with immediate- and extended-release quetiapine in a real clinical setting: a longitudinal, cohort study of 1761 patients

Abstract

Objectives: The objective of this work was to study characteristics and clinical treatment patterns of bipolar disorder (BD) patients admitted to hospital and treated with quetiapine (immediate-release [IR] or extended-release [XR] formulations). Methods: BD patients admitted to hospital and prescribed quetiapine IR were followed by linking two Swedish nationwide registries; the hospitalization and drug dispense registries [ClinicalTrials.gov identifier: NCT01455961]. The study period was from 1 January 2008, to end of 31 December 2011. Data was primarily analysed using descriptive methods. Results: Quetiapine IR was used in 1761 patients of whom 1303 subsequently switched to XR (switch XR) and 458 remained on IR (continuous IR). At baseline, Switch XR patients were younger (−3.3 years), more frequently employed (+7.1%), had higher prevalence of single depressive episodes (+6.7%) and anxiety disorders (+5.8%), lower mean daily IR dose (−19.3%) and fewer medications for somatic disorders (−7.5%) than continuous IR patients. During follow up, the number of concomitant psychiatric medications was lower in switch XR patients (−6%) and higher in continuous IR patients (+6%). Mean daily quetiapine dose was 21% higher in switch XR versus continuous IR patients. Prescriptions of lower quetiapine dosages calculated below 50 mg per day in the XR switch and IR continuous groups were seen in 8% versus 10% of the patients, respectively. Conclusions: Differential use of quetiapine XR and IR in bipolar disorder patients with different and important characteristics was demonstrated. Patients who were switched to quetiapine XR had a higher psychiatric disease burden, were younger and had a higher degree of employment. These differences demonstrate the heterogeneity among bipolar disorder patients and indicate the need in clinical practice for individualized treatment to reduce the risk for both patient and society related losses.