Comparison of sedative effects of romifidine following intravenous, intramuscular, and sublingual administration to horses

Objective-To compare sedative effects of romifidine following IV, IM, or su blingual (SL) administration in horses. Animals-30 horses that required sedation for routine tooth rasping. Procedure-Horses (n = 10/group) were given romifidine (120 mu g/kg) IV, IM, or SL. Heart rate, respiratory rate, head height, distance between the ear tips, thickness of the upper lip, response to auditory stimulation, respon se to tactile stimulation, and degree of ataxia were recorded every 15 minu tes for 180 minutes. Tooth rasping was performed 60 minutes after administr ation of romifidine, and overall adequacy of sedation was assessed. Results-IV and IM administration of romifidine induced significant sedation , but SL administration did not induce significant sedative effects. Scores for overall adequacy of sedation after IV and IM sedation were not signifi cantly different from each other but were significantly different from scor es for horses given romifidine SL. Sedative and other effects varied among groups during the first 60 minutes after drug administration; thereafter, e ffects of IV and IM administration were similar. Conclusions and Clinical Relevance-Onset of action was fastest and degree o f sedation was greater after IV, compared with IM, administration of romifi dine, but duration of action was longer after IM administration. Sublingual administration did not result in clinically important sedative effects.