PHARMACOKINETICS AND PHARMACODYNAMICS OF TRANSDERMAL DEXMEDETOMIDINE

Dexmedetomidine is a novel alpha(2)-adrenoceptor agonist that may prov ide beneficial effects as premedication for anesthesia. The pharmacoki netics and pharmacodynamics of transdermal (TD) and intravenous (IV) d exmedetomidine were studied in nine healthy male subjects in a crossov er trial. The TD preparation, containing 625 mu g of dexmedetomidine b ase, was applied on the forehead and left in place for 12 h. The IV do se (2.0 mu g.kg(-1) as dexmedetomidine hydrochloride) was administered as an infusion over 5 min. Dose-normalized total AUC values were used to calculate dexmedetomidine bioavailability. The bioavailability of dexmedetomidine from the TD preparation was 51%. However, the bioavail ability of dexmedetomidine released from the preparation was 88%. The mean terminal half-life was 3.1 h after IV and 5.6 h after TD administ ration. After TD administration, the mean maximal reductions in blood pressure (systolic/diastolic) and heart rate were 28/20 mmHg and 19 be ats.min(-1). A sedative effect was obvious within 5 min and 1-2 h afte r IV and TD administration, respectively.