Factors Related to Early Clinical Effects of Quetiapine Extended-Release: A Multinational, Prospective, Observational Study.

Background And Objectives: The first weeks of treatment with antipsychotics are important for the development of their long-term efficacy. The objective of this study was to identify factors related to early clinical effects and quality of life (QoL) improvements with quetiapine extended-release (XR).

Methods: Six hundred and sixty-five patients starting with quetiapine XR were followed up for 8 weeks (schizophrenia = 153, major depression = 200, bipolar depression = 252, other psychiatric conditions = 60). Clinical effects were assessed by the Clinical Global Impression of Change scale (CGI-C), QoL by the visual analog scale (VAS) of the EQ-5D (QoL-VAS), and adherence by the Moriksy scale. Adverse events were explored: movement disorders by the UKU and Simpson-Angus scales, weight gain by calibrated balances, and diurnal somnolence by the Epworth Somnolence Scale (ESS).

Results: The mean dose of quetiapine XR during follow-up was 195.6 ± 154.8 mg/day. CGI and QoL-VAS scores improved significantly at week 8 by 2.7 ± 0.1 points and 25.1 ± 0.9 points. Adverse events were observed in 34 and 26 % of patients at weeks 4 and 8, respectively. A significant reduction in ESS score was also observed at week 8. Factors independently associated with change in QoL-VAS ≥20 points (n = 292, 43 %) were female gender, more severe disease at baseline, higher antipsychotic dose during follow-up, and improvements in somnolence. Factors independently associated with clinically significant improvement (CGI-C ≥5, n = 610, 93 %) were greater change in QoL-VAS, less frequent movement disorders at baseline, and lack of adverse events during follow-up, especially somnolence.

Conclusions: Results from this real-setting, large observational study in Central America suggest that disease severity at baseline, gender, antipsychotic dose, and occurrence of adverse reactions has a significant impact on the early clinical effects of quetiapine XR. Clinicaltrials.gov registration number NCT02409823.