Use of quetiapine XR and quetiapine IR in clinical practice for hospitalized patients with schizophrenia: a retrospective study.

Quetiapine fumarate, a first-line treatment for schizophrenia, exists in two formulations: extended release (XR) and immediate release (IR). This naturalistic, noninterventional study evaluated use of quetiapine XR/IR among in-patients with schizophrenia [ClinicalTrials.gov identifier: NCT01214135]. Data were collected from medical records. Categorical and numerical outcomes were compared using χ(2) and t tests. Of 178 enrolled patients, 66% and 34% used quetiapine XR and IR respectively. Based on mean daily dose, XR was used as antipsychotic medication in 64% of patients compared with 40% of patients on IR (dose ≥ 400 mg/day; p = 0.002) and in higher doses than IR (494 versus 345 mg/day; p = 0.001; calculated averages). Schizophrenia was more commonly reported as reason for use of XR than IR (20% versus 0%; p = 0.0003). Patients with comorbid substance abuse or somatic disease were more likely to receive XR (p = 0.003; p = 0.03). Treatment cessation due to nonadherence was less common in patients on XR (3.4% versus 12%; p = 0.03). Polypharmacy was seen in 98% of patients. Quetiapine XR/IR usage varies in hospitalized patients with schizophrenia. XR is more often used in antipsychotic dosage; IR is more commonly used at lower doses as add-on therapy. Both quetiapine XR and IR have their place in clinical practice and provide treatment choice in schizophrenia.