Simultaneous quantification of vinblastine and desacetylvinblastine concentrations in canine plasma and urine samples using LC–APCI–MS/MS

A highly sensitive and specific liquid chromatography–atmospheric pressure chemical ionization–mass spectrometry (LC/APCI–MS/MS) method has been developed and validated for simultaneous quantification of vinblastine and its metabolite, desacetylvinblastine, in canine plasma and urine samples. Plasma and urine samples were processed by a solid phase extraction procedure. The optimal chromatographic behavior of these analytes was achieved on pentafluorophenyl (PFP) propyl analytical column (5 μm, 50 × 2.1 mm) under isocratic elution of 0.75 mL/min with a mobile phase of 5 mM ammonium acetate and methanol. The samples were analyzed in positive ion, multiple reaction monitoring mode. The calibration curves were linear over 0.125–2 ng/mL (lower calibration curve); 2–100 ng/mL (higher calibration curve) and 0.125–5 ng/mL for vinblastine and desacetylvinblastine in plasma, and over 1–2000 ng/mL and 0.5–100 ng/mL for vinblastine and desacetylvinblastine in urine samples, respectively. The limits of quantitation of vinblastine and desacetylvinblastine were 0.125 ng/mL in both matrices. The intra and interday accuracy was above 89% and precision below 8.6% for both analytes in both matrices. The developed method was successfully applied to ongoing in vivo vinblastine pharmacokinetic studies in dogs.