Population pharmacokinetics of dexmedetomidine during long-term sedation in intensive care patients.

BACKGROUND Dexmedetomidine is a highly selective and potent α(2)-adrenoceptor agonist registered for sedation of patients in intensive care units. There is little information on factors possibly affecting its pharmacokinetics during long drug infusions in critically ill patients. We characterized the pharmacokinetics of dexmedetomidine in critically ill patients during long-term sedation using a population pharmacokinetic approach. METHODS Twenty-one intensive care patients requiring sedation and mechanical ventilation received dexmedetomidine with a loading dose of 3-6 µg kg(-1) h(-1) in 10 min and a maintenance dose of 0.1-2.5 µg kg(-1) h(-1) for a median duration of 96 h (range, 20-571 h). Cardiac output (CO), laboratory and respiratory parameters, and dexmedetomidine concentrations in arterial plasma were measured. The pharmacokinetics was determined by population analysis using linear multicompartment models. RESULTS The pharmacokinetics of dexmedetomidine was best described by a two-compartment model. The population values (95% confidence interval) for elimination clearance, inter-compartmental clearance, central volume of distribution, and volume of distribution at steady state were 57.0 (42.1, 65.6), 183 (157, 212) litre h(-1), 12.3 (7.6, 17.0), and 132 (96, 189) litre. Dexmedetomidine clearance decreased with decreasing CO and with increasing age, whereas its volume of distribution at steady state was increased in patients with low plasma albumin concentration. CONCLUSIONS The population pharmacokinetics of dexmedetomidine was generally in line with results from previous studies. In elderly patients and in patients with hypoalbuminaemia, the elimination half-life and the context-sensitive half-time of dexmedetomidine were prolonged.