MEASUREMENT OF CARBAMAZEPINE AND ITS MAIN BIOTRANSFORMATION PRODUCTS IN PLASMA BY HPLC

We present a method that permits the simultaneous analysis of carbamazepine (CBZ) and its major biotransformation products, carbamazepine-10, 11-epoxide (CBZ-E) and carbamazepine-10, 11-dihydroxide (CBZ-diOH), in plasma samples. The method consists of plasma extraction in alkaline medium with NaCI added using chloroform-ethyl acetate (1:1, v/v) and later purification with n-hexane. The samples were submitted to reversed-phase chromatography (RP-18) using acetonitrile-water (3:7, v/v) as the mobile phase and detection at 220 nm. Recoveries of 62.0, 99.9, and 105.4% were obtained for CBZ-diOH, CBZ-E, and CBZ, respectively, with sensitivities of 0.32 μg/mL for CBZ-E and CBZ-diOH and of 0.64 μg/mL for CBZ. The method proved to be specific, thus permitting measurements in situations of drug combinations. © 1992, Oxford University Press. All rights reserved.