A Retrospective Study of Clinical Usage of Quetiapine XR and Quetiapine IR in Outpatients with Schizophrenia in Denmark

Objectives: The atypical antipsychotic quetiapine is a first-line treatment for schizophrenia. This non-interventional study (NCT01212575) evaluated the clinical use of its two formulations, extended release (XR) and immediate release (IR), in outpatients with schizophrenia spectrum disorder.

Methods: Patients who had received at least one dose of quetiapine XR and/or IR were included. A dosage ≥400 mg/day was defined as antipsychotic. Medical records data were collected retrospectively.

Results: Of 186 enrolled patients, 99 (53%) and 87 (47%) received quetiapine XR and IR, respectively. Use in antipsychotic dosage was seen for 89% XR versus 63% IR patients (mean daily dose ≥400 mg/day; p < 0.0001). 75% XR and 53% IR patients used dosages ≥600 mg/day (p = 0.0019). Quetiapine XR was used at higher mean daily dosages than IR (748 vs 566 mg/day; p = 0.006). Forty-three patients (23%) used both formulations concomitantly; 55 patients (30%) used either XR or IR. Quetiapine IR was used as-needed in 44 patients (23%); one patient used XR as-needed.

Conclusions: Quetiapine XR was used more often in higher (antipsychotic) dosages; quetiapine IR more frequently on an as-needed administration basis. Concomitant use was seen. These findings probably reflect the different profiles of XR/IR and advocate the need for both formulations to offer treatment choice.