Duloxetine serum concentrations and clinical effects. Data from a therapeutic drug monitoring (TDM) survey.

ABSTRACT

INTRODUCTION: The aim of this study was to relate drug concentrations in serum and clinical effects in patients treated with the new antidepressant duloxetine. METHODS: Data were obtained from a newly established therapeutic drug monitoring (TDM) survey. Duloxetine was measured using HPLC with UV detection and clinical effects by the clinical global impressions (CGI) scale for improvement. RESULTS: The study included 103 depressed inpatients (69% female). Patients under duloxetine monotherapy who were very much improved according to CGI had significantly (p<0.05) higher serum levels than patients with moderate, minimal or lacking improvement (mean+/-SD and range, 93+/-53 ng/mL and 30-182 ng/mL and 47+/-39 ng/mL and 5-178 ng/mL, respectively). Daily doses were similar in the two groups (76+/-27 vs. 83+/-27 mg/d). Receiver operating characteristics (ROC) curve analysis revealed significant predictive properties of duloxetine serum levels (p=0.011) for improvement with a lower threshold concentration of duloxetine of 58 ng/mL. DISCUSSION: The findings indicate that therapeutic drug monitoring of duloxetine and titration to steady state serum concentrations above 58 ng/mL is useful for treatment optimization.