DIFFERENTIATION BETWEEN NAPROXEN, NAPROXEN-PROTEIN CONJUGATES, AND NAPROXEN-LYSINE IN PLASMA VIA MICELLAR ELECTROKINETIC CAPILLARY CHROMATOGRAPHY - A NEW APPROACH IN THE BIOANALYSIS OF DRUG TARGETING PREPARATIONS

Pharmacotherapy through the targeting of drugs is a promising new appr oach that requires adequate analytical methods capable of differentiat ing between the free drug the drug carrier, and metabolites. Using mic ellar electrokinetic capillary chromatography (MECC), we report the se paration of naproxen (NAP) from NAP covalently coupled to human serum albumin or to mannosylated serum albumin and the metabolite naproxen-l ysine. An assay for selective analysis of the different forms of NAP b y direct plasma injection was developed with salicylate as internal st andard and solute detection by laser-induced fluorescence. Compared wi th previously applied techniques, including HPLC and total plasma fluo rescence, MECC offers the advantage that free and covalently bound NAP can be differentiated in one nut and can be accurately monitored in m icroliter quantities of plasma. Summation of all NAP equivalents deter mined by MECC revealed data that compare well with those produced by t otal plasma fluorescence and HPLC.