REVERSAL OF MEDETOMIDINE-INDUCED SEDATION IN REINDEER (RANGIFER TARANDUS TARANDUS) WITH ATIPAMEZOLE INCREASES THE MEDETOMIDINE CONCENTRATION IN PLASMA

The pharmacokinetics of two potent az-adrenoceptor agents that can be used for immobilization (medetomidine) and reversal (atipamezole) of t he sedation in mammals, were studied in three reindeer (Rangifer taran dus tarandus) in winter and again in summer, Medetomidine (60 mu g/kg) was injected intravenously (i.v.), followed by atipamezole (300 mu g/ kg) intravenously 60 min later, Drug concentrations in plasma were mea sured by HPLC. The administration of atipamezole resulted in an immedi ate 2.5-3.5 fold increase in the medetomidine concentration in plasma. Clearance for medetomidine (median 19.3 mL/min.kg) was lower than cle arance for atipamezole (median 31.0 mL/min.kg). The median elimination half-lives of medetomidine and atipamezole in plasma were 76.1 and 59 .9 min, respectively, The animals became resedated 0.5-1 h after the r eversal with atipamezole, Resedation may be explained by the longer el imination half-life of medetomidine compared to atipamezole.