Effects of Dexmedetomidine on the Pharmacokinetics of Parecoxib and Its Metabolite Valdecoxib in Beagles by UPLC-MS/MS.

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A sensitive and reliable ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was developed for the simultaneous determination of parecoxib and its metabolite valdecoxib in beagles. The effects of dexmedetomidine on the pharmacokinetics of parecoxib and valdecoxib in beagles were studied. The plasma was precipitated by acetonitrile, and the two analytes were separated on an Acquity UPLC BEH C18 column (2.1 mm × 50 mm, 1.7 μm); the mobile phase was acetonitrile and 0.1% formic acid with gradient mode, and the flow rate was 0.4 mL/min. In the negative ion mode, the two analytes and internal standard (IS) were monitored by multiple reaction monitoring (MRM), and the mass transition pairs were as follows: m/z 369.1 → 119.1 for parecoxib, m/z 313.0 → 118.0 for valdecoxib, and m/z 380.0 → 316.0 for celecoxib (IS). Six beagles were designed as a double cycle self-control experiment. In the first cycle, after intramuscular injection of parecoxib 1.33 mg/kg, 1.0 mL blood samples were collected at different times (group A). In the second cycle, the same six beagles were intravenously injected with 2 μg/kg dexmedetomidine for 7 days after one week of washing period. On day 7, after intravenous injection of 2 μg/kg dexmedetomidine for 0.5 hours, 6 beagle dogs were intramuscularly injected with 1.33 mg/kg parecoxib, and blood samples were collected at different time points (group A). The concentration of parecoxib and valdecoxib was detected by UPLC-MS/MS, and the main pharmacokinetic parameters were calculated by DAS 2.0 software. Under the experimental conditions, the method has a good linear relationship for both analytes. The interday and intraday precision was less than 8.07%; the accuracy values were from -1.20% to 2.76%. Cmax of parecoxib in group A and group B was 2148.59 ± 406.13 ng/mL and 2100.49 ± 356.94 ng/mL, t1/2 was 0.85 ± 0.36 h and 0.85 ± 0.36 h, and AUC(0‐t) was 2429.96 ± 323.22 ng·h/mL and 2506.38 ± 544.83 ng·h/mL, respectively. Cmax of valdecoxib in group A and group B was 2059.15 ± 281.86 ng/mL and 2837.39 ± 276.78 ng/mL, t1/2 was 2.44 ± 1.55 h and 2.91 ± 1.27 h, and AUC(0‐t) was 4971.61 ± 696.56 ng·h/mL and 6770.65 ± 453.25 ng·h/mL, respectively. There was no significant change in the pharmacokinetics of parecoxib in groups A and B. Cmax and AUC(0 − ∞) of valdecoxib in group A were 37.79% and 36.19% higher than those in group B, respectively, and t1/2 was increased from 2.44 h to 2.91 h. Vz/F and CLz/F were correspondingly reduced, respectively. The developed UPLC-MS/MS method for simultaneous determination of parecoxib and valdecoxib in beagle plasma was specific, accurate, rapid, and suitable for the pharmacokinetics and drug-drug interactions of parecoxib and valdecoxib. Dexmedetomidine can inhibit the metabolism of valdecoxib in beagles and increase the exposure of valdecoxib, but it does not affect the pharmacokinetics of parecoxib.