Practical Standing Chemical Restraint of the Horse

1. Introduction
Many surgical and medical procedures can be accomplished in the standing horse if appropriate combinations of physical and chemical restraint are employed. The ability to perform procedures in the standing position is more important in the horse than in other species because of the greater risk of complications associated with anesthesia in the horse.¹  The goal of most standing restraint is to produce a quiet, calm horse that is immobile and does not react to stimuli or manipulation. Analgesia should be provided if the intended procedure is expected to be painful.

There are nine drugs approved for use in horses for standing chemical restraint: acepromazine, butorphanol, chloropent, detomidine, pentazocine, promazine, romifidine, triflupromazine, and xylazine. Of these, only five drugs (acepromazine, butorphanol, detomidine, romifidine, and xylazine) are commercially marketed by pharmaceutical houses. Other drugs, such as morphine and fentanyl, are used with some frequency for standing chemical restraint but are not labeled for use in the horse. No single drug produces “ideal” standing chemical restraint in every horse. Although the majority of sedative and analgesic drugs used for restraint are labeled for use as “sole” agents, the majority of equine veterinarians use them in combination with the goal of optimizing the onset, quality, and duration of the alteration in mental state while minimizing potentially deleterious side effects. Many combinations are recommended in the literature, but relatively few have been rigorously studied scientifically. The potential number of combinations for the nine approved drugs (511 combinations) and the five commercially marked drugs (31 combinations) suggests that it is unlikely that such studies will be completed. [...]