Chemical restraint for surgery in the standing horse.

Chemical restraint can be a useful pharmacologic tool to assist the veterinarian performing surgery in the standing horse. The agents discussed impose minimal adverse side effects and are considered relatively safe when administered in the doses described. Acetylpromazine, the most widely used tranquilizer, produces mild sedation but no analgesia. The use of tranquilizers for surgical procedures requires the combined use of either a local anesthetic technique or a sedative-hypnotic or opiate to provide analgesia. Sedative-hypnotics such as xylazine and detomidine or opiates such as morphine and butorphanol are commonly used. The sedative-hypnotics also can induce deep CNS depression and may be sufficient alone for many procedures. Opiates may be used to supplement the analgesia produced by sedative-hypnotics or provide analgesia to the tranquilized horse. Opiates are not useful alone because of their potential to cause CNS excitement in the horse. The combination of detomidine and butorphanol is probably the most effective drug combination to facilitate painful surgery in the standing horse.