*Resident TSenior Staff Anesthesiologist $Clinical Research Manager, Orion Corpo- ration, Farmos Research Center PAssociate Professor Address reprint requests to Dr. Aho at the Department of Anesthesia, Women’s Hospi- tal, Helsinki University Central Hospital, IHaartmaninkatu 2, SF-00290 Helsinki, Fin- !and. Received for publication May 13, 1992; re- vised manuscript accepted for publication November 16, 1992. 0 1993 Butterworth-Heinemann , Clin. Anesth. 5:19&203, 1993. Departments of ,4nesthesia, Women’s PIospital, Helsinki &‘niversity Gent& Hospi- tai, and Welsinki University, Helsinki, Finland; Orion Corporation, Farmos Re- search Center, Turku, Finland. Study Objective: To evaluate the effects ojdexmedeto~midine, an alpha-2 zgorazst, as an intravenous sedative drug and the effects of atipamezole, an alpha-2 antagonist, on recovery. Design: Randomized, double-blind study with three parallel groups. An ofien dose- &ding study preceded it to opti,mize the atipamezole dose. Setting: Outpatient operating room at the gynecologic and obstetric university h,ospital in Helsinki, Finland. Patients: Seventy-two healthy women scheduled for legal termination of pregnancy. Interventions: Patients were assigned to one of three groups of 24 patients each to receive either dexmedetomidine 2 pglkg and atipamezole 50 pglkg; dex~nedetom~dine 2 pglkg and saline; or midazolam 0.15 mglkg and saline. In addition to parace-rvical block, each patie& received two dzyferent study drugs: study drug 1 was a sedative agent {either dexmedetomidine or midazolam), administered before the procedure. rf the sedation was not deep enough and the patient reacted to the procedure, a low dose of propofol was administered. Stu,dy drug 2 was a reversing agent or a placebo, adrrLinis- tered following the procedure. Measurements and ain Results: The mean time to regain consciousness was shorter in the dexmedetomidine-atipumezole and the dexmedetomidine-saline groups compared zuith the midazolam group. Postoperatiue sedation, tested both by subjective and objective assessments, decreased more quickly in the dexmedetomidi~e-atipa~~~o~e group compared zuith the dexmedetornidine-saline and the midazolam groups. Gonclusion: Ati~a.mezole is an effective antagonist for reversing psychomotor impair- ment following dexmedetomidine sedation. Alpha-adrenergic agonists; alpha-adrenergic antagonisrs; atipamezole; anesthesia, hemodynamics; dexmedetomidine; receptors, alpha-2-adrenergic; sympathetic nervous system. J. Glin. Anesth., vol. 5, May/ June 1993