Question: I had Quarter Horses for more than 30 years, but now I am the proud owner of three rescues: an 11-year-old 38-inch pony, a 6-year-old Miniature Horse, and a 14-year-old Miniature Donkey. After I first brought them home, I asked the veterinarian to check their teeth, and they needed to be floated. She sedated them to do it. It took two doses before she could handle the donkey.
Last year, they needed to be done again. A different veterinarian came out, and he also sedated them. The donkey again required a second dose, but this time, as soon as it was administered, he went down hard and started thrashing his legs, groaning and moaning. The veterinarian went for the shot to counteract the sedative, and the donkey calmed down quickly after it was administered. But during the reaction he skinned up his legs and his head, and it was several days before he started acting normal. The experience was truly terrifying.
My question is, why are veterinarians so quick to use sedatives instead of trying a nose twitch? Drugs seem a rather drastic way to go, especially when there is no way to know when a bad reaction will happen. I realize no single solution will work for every animal and that some may need to be sedated, but why not try the less severe route first?
I never had trouble with nose twitches with my large horses. When the twitch was put on they calmed down immediately and when it came off, all was done---no recovery time, no harm done; just rub their nose and let them loose.
Answer: To answer your question, we need to consider the following: the goals of equine dentistry, the difference in physiology between donkeys (especially mini donkeys) and horses, and the pharmacologic and actual effects of the most commonly used intravenous sedatives versus the mechanical and physiological effects of the nose twitch.
Up-to-date equine dentistry requires a complete examination of the oral cavity including the occlusal, inner and outer surfaces of the teeth; the soft tissues of the tongue, palate, cheeks and gums; the spaces between the teeth; and the cavities of the occlusal surfaces. This requires the use of a full-mouth speculum, a light source, an explorer, picks and a flushing mechanism. The work may include picking, flushing and establishing dental equilibrium. All of this can take 30 minutes or more, start to finish.
Most veterinarians prefer to use a sedative during dental procedures. The goal of sedation is to induce muscle relaxation, reduce the horse’s anxiety and provide some pain relief so the horse will stand quietly and comfortably for the duration of the work. This is safer for both the horse and the veterinarian.
The most commonly used sedatives for dentistry are detomidine, an alpha-adrenergic agonist class medication, and butorphanol, a synthetic opioid drug. Detomidine provides muscle relaxation and some pain relief. Administered intravenously, this drug takes effect in three to five minutes and can last 45 minutes to an hour. A low dose is used initially and repeated as needed, often in combination with butorphanol. Low-dose combination sedation may be safer and more effective than higher doses of either drug.
Butorphanol is often used in conjunction with alpha-agonists like detomidine. It is effective in three to five minutes after IV administration and lasts one to two hours. Butorphanol provides additional sedation and analgesia but seems to stabilize the standing posture of the horse. Again, the combination of the drugs allows the use of lower doses of each.
Abnormal reactions are rare. Leakage or inadvertent injection into an artery can cause sudden recumbency with paddling, as you described. Any history of sensitivity to sedation with different drugs is important, so be sure to tell any future veterinarians about this episode with your donkey.
A review article from Texas A&M College of Veterinary Medicine explained that the physiology of donkeys (Miniature Donkeys especially) is different from that of horses and that their metabolism leads to a shorter interval of effectiveness for many sedatives. They may require more sedation per pound and more frequent administration of the drug than do horses. Mules tend to be in between horses and donkeys in response to sedation.
As for why most veterinarians choose not to use twitches to restrain horses for dental procedures, time is a major factor. Sue McDonnell, PhD, from the University of Pennsylvania, described the physical, mental and physiologic effects of the nose twitch, a device with a loop or clamp that is used to squeeze the upper lip of the horse. According to McDonnell, a nose twitch applied by an experienced handler without undue stress and commotion causes distraction from pain for three to five minutes. For only about the next five to 10 minutes, the horse’s levels of beta- endorphins, which act as a pain-relieving sedative, are doubled. At 12 to 15 minutes after the application of the twitch, the endorphins are no longer elevated, and the “blow up” stage is reached. If the twitch is removed before that point and a waiting period is allowed, it could be effectively reapplied.
In addition, veterinarians need full access to the mouth during dental examinations or procedures, and a twitch can get in the way. Further, using the twitch humanely requires a second person to be standing close by, crowding the veterinarian and potentially getting in harm’s way if anything goes wrong.
In conclusion, most veterinary equine dentists believe that intravenous sedation is the best way to control a horse during dental procedures. This method safely causes relaxation with less discomfort and anxiety to the patient, while allowing for a more thorough examination with enough time for any needed treatment. A nose twitch does not.
Jim Latham, Jr, DVM
Mill Creek Veterinary Service
Jim Latham, Jr, DVM, has been a practicing equine veterinarian for 42 years and has been a guest lecturer in equine dentistry with partner, Patty Latham, DVM, at Colorado State University’s College of Veterinary Medicine and Biomedical Sciences as well as at CSU’s Equine Science program. The Lathams now maintain an equine dental practice in Archuleta County, Colorado, when not riding in the high country.
This article was originally published in EQUUS 485, February 2018