Dexmedetomidine is a potent alpha2-adrenoceptor agonist with 8 times higher affinity for the alpha2-adrenoceptor than clonidine. Dexmedetomidine has shown sedative, analgesic and anxiolytic effects after intravenous administration to healthy volunteers or postsurgical patients in the intensive care unit. Dexmedetomidine produced a predictable haemodynamic decline (dose-dependently decreased arterial blood pressure and heart rate) in postsurgical patients coinciding with reductions in plasma catecholamines. In phase III clinical trials, dexmedetomidine 0.2 to 0.7 microg/kg/h produced clinically effective sedation and significantly reduced the analgesic requirements of postsurgical ventilated intensive care unit patients. There was no clinically apparent respiratory depression after cessation of assisted ventilation. Dexmedetomidine produced rapid and stable sedation in postsurgical ventilated patients while maintaining a high degree of patient rousability and anxiety reduction. Dexmedetomidine was well tolerated in phase III studies. The most frequently observed adverse events were hypotension, bradycardia and nausea.