Therapeutic drug monitoring of albendazole: Determination of albendazole, albendazole sulfoxide, and albendazole sulfone in human plasma using nonaqueous capillary electrophoresis

A nonaqueous capillary electrophoretic method (NACE) for the fast determina tion of plasma levels of albendazole (ABZ), albendazole sulfoxide (ABZSO), and albendazole sulfone (ABZSO(2)) is described. TI-le assay is based upon liquid/liquid extraction of these compounds using dichloromethane at pH 10. 2 (recovery between 63 and 98%), followed by a NACE separation performed wi thin 8 min employing a 0.036 M berate buffer (apparent pH 9.9) in a mixture of methanol and N-methylfermamide (1:3) and on-column absorbance detection at 280 nm. Using 0.5 mt of plasma and extract reconstitution in 200 mu L N -methylformamide, drug levels between 1.0-10 mu M were found to provide lin ear calibration graphs. Intraday and interday imprecisions evaluated from p eak area ratios (n = 5) were < 10% and < 12%, respectively. Corresponding i mprecisions of detection times (n = 5) were < 1% and < 6%, respectively. Th e limit of detection (LOD) for ABZ, ABZSO and ABZSO(2) was 8 x 10(-7) M. Th e reliability of the method developed was verified via analysis of 45 plasm a samples obtained from patients treated with ABZ. Good agreement was obtai ned between the levels of ABZSO and those determined by routine HPLC. ABZ w as found to be undetectable in all patient samples, whereas the levels of A BZSO(2) were below or close to LOD.