Analytical method development for the simultaneous quantitation of dexmedetomidine and three potential metabolites in plasma

Dexmedetomidine, a novel alpha(2)-adrenergic receptor agonist, is being developed as an anesthetic adjunct for perioperative use. An assay method has been developed for the sensitive quantitation of dexmedetomidine and three metabolites in plasma: MPV-1305, MPV-1306 and MPV-1709. The method involves solid-phase extraction (C-18 cartridge) of dexmedetomidine and metabolites followed by a two-step derivatization. The first step utilized BF3-MeOH to simultaneously mask a primary alcohol in MPV-1305 and a carboxylic acid in MPV-1306. The second step applied PFB-Cl to derivatize the imidazole ring for sensitive detection of these compounds by GC-negative chemical ionization MS at pg/ml concentrations. MPV-1709 was not derivatized in the process and was detected by GC-positive chemical ionization MS. Optimization of extraction and derivatization is discussed. The method is suitable for quantitation of dexmedetomidine, MPV-1305, MPV-1306 and MPV-1709 over concentration ranges of 0.1-40, 0.5-100, 0.5-100 and 1.0-500 ng/ml, respectively. The method showed excellent specificity, linearity and sensitivity and is useful for profiling the pharmacokinetic disposition of these compounds.