Determination of reboxetine, a recent antidepressant drug, in human plasma by means of two high-performance liquid chromatography methods

Reboxetine is a new norepinephrine reuptake inhibitor (NRI) drug recently introduced in the therapy for depressed patients. It is effective in the treatment of severe depression and safer to use than traditional tricyclic antidepressants. In this paper an original high-performance liquid chromatography (HPLC) method with ultraviolet detection for the determination of reboxetine in human plasma is described. It uses a C8 reversed-phase column and a mobile phase composed of acetonitrile and aqueous tetramethylammonium perchlorate. For the analysis of plasma samples containing very low levels of reboxetine, another HPLC method with fluorimetric detection was developed (limit of quantitation, LOQ=11 ng ml−1; limit of detection, LOD=4 ng ml−1). The fluorimetric method is based on precolumn derivatisation of reboxetine with 9-fluorenylmethyl chloroformate. An accurate sample pretreatment of human plasma samples has been implemented by means of solid-phase extraction (SPE) on Oasis HLB (hydrophilic–lipophilic balance) cartridges with very high extraction yields (>95%). Both methods were applied to the analysis of plasma samples from depressed patients undergoing therapy with reboxetine and gave satisfactory results in terms of precision (RSD<4.5%) and accuracy (mean recovery>94%).