Serum concentrations of fluoxetine in the clinical treatment setting

This article discusses fluoxetine serum concentrations as displayed in a cl inical setting. A racemic serum fluoxetine and norfluoxetine high-performan ce liquid chromatography method, including ultraviolet light detection, was used for routine therapeutic drug monitoring (TDM) purposes. In all, 508 s amples were analyzed. For the scientific investigation, predefined inclusio n and exclusion criteria were applied and 150 samples representative of tro ugh values in steady-stale conditions with essential clinical information p rovided on the assay request forms were evaluated, Fluoxetine plus norfluox etine concentration-to-dose (C/D) ratio showed Gaussian distribution. Inter individual coefficients of variation of fluoxetine and norfluoxetine serum concentrations after different doses were found to be 40-63%. Intraindividu al fluoxetine TDM variability was low. The Spearman rank correlation coeffi cient for fluoxetine and norfluoxetine C/D ratios in first and second sampl es was 0.68. Minor increases in norfluoxetine C/D and fluoxetine plus norfl uoxetine C/D ratios were found in elderly patients compared with younger ad ult patients. A higher body-mass index was associated with minor decreases in fluoxetine and fluoxetine plus norfluoxetine C/D ratios. New fluoxetine pharmacokinetic data are added to the results from earlier phases of drug d evelopment. Moreover, the results of this study support the usefulness of a fluoxetine TDM procedure for individual dose optimization, detection of dr ug interactions, and assessments of patient compliance.