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DETERMINATION OF URAPIDIL HYDROCHLORIDE IN RABBIT PLASMA BY LC-MS-MS AND ITS APPLICATION TO A PHARMACOKINETIC STUDY

A sensitive and selective liquid chromatography tandem mass spectrometry (LC-MS-MS) method for determination of urapidil hydrochloride in rabbit plasma was developed and validated. After addition of doxapram hydrochloride as the internal standard (IS), protein precipitation by 10% trichloroacetic acid was used as the sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 mm × 50 mm, 3.5 μm) column with acetonitrile-water as the mobile phase with gradient elution. Electrospray ionization (ESI) source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used to quantification using target fragment ions m/z 387.9 → 204.6 for urapidil hydrochloride and m/z 378.9 → 291.8 for the IS. Calibration plots were linear over the range of 5–1000 ng/mL for urapidil hydrochloride in plasma. Lower limit of quantitation (LLOQ) for urapidil hydrochloride was 5 ng/mL. Mean recovery of urapidil hydrochloride from plasma was in the range 93.5%–96.4%. RSD of intra-day and inter-day precision were both less than 12%. This developed method is successfully used in pharmacokinetic study of urapidil hydrochloride in rabbit.