Relationship between serum concentration and clinical response of quetiapine in adolescents and adults with bipolar disorders in acute stage: a prospective observational study

Background: It is found that there are great differences in the efficacy of quetiapine at the same dose in many patients with bipolar disorders. Therefore, therapeutic drug monitoring (TDM) is a valuable tool for guiding treatment with quetiapine. The aims of this study were to assess the relationship between serum concentration and clinical response of quetiapine in adolescents and adults with bipolar disorders in acute stage. Methods: The study design was prospective and observational. Within the naturalistic setting of a routine TDM service at the First Affiliated Hospital, Zhejiang University School of Medicine. Psychiatric symptoms were assessed using the HAMD (Hamilton Depression Scale), YRMS (Young manic rating scale) and CUDOS-M (Clinically Useful Depression Outcome Scale-Mixed Subscale). The decline of HAMD and YMRS scores was were used to assess clinical outcome of bipolar disorders respectively. Results: 169 inpatients (23.7 % male, 76.3 % female) were enrolled in the study. We found that there was a strong correlation between quetiapine serum concentrations and clinical outcomes (rs = 0.702, p < 0.001). While, quetiapine daily dose was not correlated with clinical outcome. We found that when the quetiapine serum level is >146.85 ng/ml in depression episodes patients could obtain a satisfactory treatment effect after 2 weeks of hospitalization. Conclusions: We found a significant positive relationship between serum concentration and clinical outcome, and also determined the serum concentration of quetiapine for the treatment of bipolar depression.