A simple and rapid liquid chromatography/tandem mass spectrometry (LC-MS/MS) method has been developed and applied for estimation of valganciclovir concentration levels in dog plasma after administration of valganciclovir extended release tablets (450 mg) and Valcyte® immediate release tablets (450 mg). Valganciclovir exposure in dogs is low hence ganciclovir was monitored instead of valganciclovir. The drug and internal standard, ISTD (Trospium HCl) were extracted from plasma by protein precipitation technique. The analytes were separated using a mobile phase of ammonium formate (10 mM) and organic mixture containing acetonitrile and methanol (20:80, v/v) on Zorbax SB C18, 75 x 2.1 mm, 3.5 µm with guard column at a flow rate of 0.3 ml/min and analyzed by a triple-quadrupole mass spectrometer in positive ion multiple reaction monitoring (MRM) mode at transitions (m/z) of 355.4152.2 for valganciclovir and 392.2182 for ISTD, respectively. The total chromatographic run time was 3.5 min and the assay exhibited a linear dynamic range of 0.039 -10 ng/ml in dog plasma. The developed method was successfully employed to support the bioavailability / pharmacokinetic study of valganciclovir formulations in dogs.
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