This research determined the safety and efficacy of two small-dose infusions of dexmedetomidine by evaluating sedation, analgesia, cognition, and cardiorespiratory function. Seven healthy young volunteers provided informed consent and participated on three occasions with random assignment to drug or placebo. Heart rate, blood pressure, respiratory rate, ETCO(2), O(2) saturation, and processed electroencephalogram (bispectral analysis) were monitored. Baseline hemodynamic measurements were acquired, and psychometric tests were performed (visual analog scale for sedation; observer's assessment of alertness/sedation scale; digit symbol substitution test; and memory). The pain from a 1-min cold pressor test was quantified with a visual analog scale. After a 10-min initial dose of saline or 6 microg. kg(-1). h(-1) dexmedetomidine, volunteers received 50-min IV infusions of saline, or 0.2 or 0.6 microg. kg(-1). h(-1) dexmedetomidine. Measurements were repeated at the end of infusion and during recovery. The two dexmedetomidine infusions resulted in similar and significant sedation (30%-60%), impairment of memory (approximately 50%), and psychomotor performance (28%-41%). Hemodynamics, oxygen saturation, ETCO(2), and respiratory rate were well preserved throughout the infusion and recovery periods. Pain to the cold pressor test was reduced by 30% during dexmedetomidine infusion. Small-dose dexmedetomidine provided sedation, analgesia, and memory and cognitive impairment. These properties might prove useful in a postoperative or intensive care unit setting. IMPLICATIPNS: The alpha(2) agonist, dexmedetomidine, has sedation and analgesic properties. This study quantified these effects, as well as cardiorespiratory, memory and psychomotor effects, in healthy volunteers. Dexmedetomidine infusions resulted in reversible sedation, mild analgesia, and memory impairment without cardiorespiratory compromise.