Is the evaluation of early symptom decrease and serum drug levels predictive for response in depressed patients?

Introduction: Therapeutic drug monitoring is considered as an important tool to enhance treatment efficiency and control of side effects. With respect to antidepressants, there is still a huge heterogenity regarding the published literature on the association of antidepressant blood levels and treatment response. Limitations of the published data are the small sample sizes and the nonstandardized antidepressant treatment regimes. In this study, we aimed at evaluating the predictive relevance of combining TDM and early response to monotherapy with venlafaxine after two weeks in depressed patients treated according to a standardized stepwise drug treatment algorithm. Methods: 189 caucasian participants of the third phase of the German Algorithm Project (GAP3) received continous standardized evaluation of clinical response and serum drug levels every 2 weeks and venlafaxine serum levels could be measured under steady state conditions. We tested the following hypotheses: 1. Response to antidepressive treatment can be more accurately predicted by the combination of symptom decrease after 2 weeks of antidepressant monotherapy and TDM. 2. Antidepressant responders show more frequently middle-range serum levels, while nonresponders present more frequently extreme serum levels. Results and discussion: Data analyses are still ongoing. Results regarding the value and clinical feasibility of a predictive indicator based on early symptom decrease and serum drug levels are awaited.

This study was supported by Wyeth