A blinded crossover study design to evaluate midazolam as an adjunct for equine standing sedation for routine oral examinations

This study aimed to evaluate the effects of including midazolam to a common equine standing sedation protocol for routine oral examination. Twelve horses underwent two examinations at least seven days apart. Horses were randomly assigned to receive midazolam intravenously (IV) (0.02mg/kg) or a placebo injection of saline (2-2.5mL IV). Five minutes later, detomidine (0.01mg/kg) and butorphanol (0.01mg/kg) were administered IV and horses were placed in standing stocks. A veterinarian blinded to the treatment protocol used a descriptive scoring system to assess degree of ataxia, acceptance of speculum, chewing on the speculum, headshaking, tongue movement, resistance to palpation, and eye appearance as related to the grimace score. During each examination, additional sedation of IV detomidine (0.006mg/kg) and butorphanol (0.006mg/kg) was administered at the discretion of the blinded practitioner to facilitate safe examination. At the second examination horses received the opposite treatment protocol and, following examination, a routine occlusal adjustment. Scores were compared using JMP software with a repeated measures mixed effects model, treatment as a fixed effect and horse and horse/treatment interaction as random effects. Significance was set at P<0.05. There were no significant differences in any of the single or overall sedation scores between treatment groups or within individual horses (P=0.3). Trends towards improvement of some assessed characteristics of sedation, including decreased tongue movement and less resistance to acceptance of speculum were observed. The use of midazolam may prove beneficial for routine oral examination, as well as other standing procedures, with no obvious undesired side effects.