Assessment of the sedative effects of dexmedetomidine, an alpha 2-adrenoceptor agonist, with analysis of saccadic eye movements.

Single intravenous doses (0.5 microgram/kg and 1.0 microgram kg) of dexmedetomidine (4(5)-(1-(2,3-dimethylphenyl)ethyl)imidazole), a selective alpha 2-adrenoceptor agonist, and saline placebo were administered to six healthy volunteers (4 males and 2 females) in a double-blind, placebo-controlled cross-over study. The effects on vigilance were assessed using both subjective estimation (visual analogue scale, VAS) and objective tests (critical flicker fusion frequency, CFF; the Maddox wing; saccadic eye movement analysis). Dose-dependent subjective sedation was seen in VAS measurements, and impairment of vigilance was observed in CFF, Maddox wing and peak saccadic velocity, while saccade latency was not influenced by dexmedetomidine. The changes in vigilance were concurrent with moderate reductions in blood pressure and heart rate. CFF, the Maddox wing and peak saccadic velocity all proved sensitive in the assessment of sedation induced by dexmedetomidine.