Evaluation of the muscular relaxant effect of dexmedetomidine or medetomidine in cats

摘要

The alpha_2 adrenoceptor agonist medetomidine (MED) is an equal racemic mixture of two enantiomers, dexmedetomidine (DEX) and levomedetomidine (LEV); the LEV enantiomer is generally considered to be pharmacologically inactive, whereas the DEX enantiomer is active (Virtanen et al. 1988; MacDonald et al. 1991; Savola and Virtanen 1991). Clinical studies in dogs and cats have shown that the pharmacodynamic effects of DEX are twice as potent as the MED racemic mixture, therefore DEX is administered at half the dose of MED for sedation; as for MED, the sedative and analgesic effects of DEX are antagonised by atipamezole (Cullen 1996; Ansah et al. 1998, 2000; Kuusela et al. 2000; Mendes et al. 2003; Granholm et al. 2006). DEX has been approved for clinical use in dogs and cats in Italy since 2008, and we immediately started to use it for dog and cat sedation. The sedation effect of DEX in the dog is similar to that of MED, whereas the muscular relaxant effect in the cat was lower than that of MED. The aim of this study was to evaluate and compare the muscular relaxant effects in cats following treatment with DEX or MED at bioequivalent doses.