Pharmacokinetics of dexmedetomidine after intravenous administration of a bolus to cats

Objective-To characterize the pharmacokinetics of dexmedetomidine after IV administration of a bolus to conscious healthy cats. Animals-5 healthy adult spayed female cats. Procedures-Dexmedetomidine was administered IV as a bolus at 3 doses (5, 20, or 50 mu g/kg) on separate days in a random order. Blood samples were collected immediately before and at various times for 8 hours after drug administration. Plasma dexmedetomidine concentrations were determined with liquid chromatography-mass spectrometry. Compartment models were fitted to the concentration-time data by means of nonlinear regression. Results-A 2-compartment model best fit the concentration-time data after administration of 5 mu g/kg, whereas a 3-compartment model best fit the data after administration of 20 and 50 mu g/kg. The median volume of distribution at steady-state and terminal half-life were 371 mL/kg (range, 266 to 435 mL/kg) and 31.8 minutes (range, 30.3 to 39.7 minutes), respectively, after administration of 5 mu g/kg; 545 mL/kg (range, 445 to 998 mL/kg) and 56.3 minutes (range, 39.3 to 68.9 minutes), respectively, after administration of 20 mu g/kg; and 750 mL/kg (range, 514 to 938 mL/kg) and 75.3 minutes (range, 52.2 to 223.3 minutes), respectively, after administration of 50 mu g/kg. Conclusions and Clinical Relevance-The pharmacokinetics of dexmedetomidine was characterized by a small volume of distribution and moderate clearance and had minimal dose dependence within the range of doses evaluated. These data will help clinicians design dosing regimens once effective plasma concentrations are established.