Written by: Teresa Pitman

Hear from veterinarians and horse owners about the pros and cons of using sedatives.

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Pam Mackenzie photo

For some people, using sedatives is a routine part of horse management, but others contend that they are used too often, and not necessary in most cases. Get advice from experts to help inform your decisions.

Sedation for Horses

Norah Perkins’ mare, Arden, hates veterinarians. “She can spot a vet a mile away,” she said. “So, we usually sedate her even for routine vaccinations – for the protection of the vet, really, who naturally doesn’t want to be kicked or bitten.”

Arden’s hatred of vets may be exceptional, but for many horse owners, sedatives and calming agents are an important tool for managing their horses in difficult situations when the horse might otherwise become a danger to others – or to himself. These medications are often used in horses to deal with situations where the horse might become anxious or aggressive: trailering, using clippers, or having teeth floated, for example.

Dr. Trish Dowling, of the Western College of Veterinary Medicine, explained that there are two main categories of drugs used for this purpose in horses: the alpha-2 adrenergic agonists, which are prescription medications that are given by injection (xylazine, detomidine, romefidine) and must be obtained from a veterinarian; and the phenothiazines (usually acepromazine), which can be given by injection or in granules added to feed and do not require a prescription.

The alpha-2 adregenic agonists (A2As) work more quickly, taking effect within five minutes, so tend to be preferred by vets. They wear off within 30 to 60 minutes. A2As are often recommended for procedures that might cause the horse pain, because they have an analgesic effect, and are often used in horses with colic.

Side effects include salivation, sweating, diarrhea, elevated blood glucose, decreased intestinal motility, and the risk of early labour with retained placenta, if given to a pregnant mare in the last trimester of pregnancy. These drugs should not be used with horses who have certain health problems including heart disease, respiratory dysfunction, seizures, or those who are in shock. Further, the heart rate is dramatically slowed, and some horses will faint after begin given a dose.

Dowling stressed the importance of having a vet oversee any use of sedatives, and feels that if the injectable form is used, a vet should administer the drug. ‘If either class of drug is accidentally given in the carotid artery rather than the jugular vein, it’s a bad wreck,’ she said.

She cautioned that “if the animal is already agitated or excited, it’s difficult for these drugs to work. They do also reduce normal inhibitions, so a horse that usually wouldn’t kick you may kick you when sedated.”

Acepromazine takes about 30 minutes to take effect and will last eight hours or longer. It does not relieve pain, so should not be used to control the horse for painful procedures. Dowling pointed out ‘it’s important not to ‘trust’ the sedation. If you startle the horse or cause enough pain, he can override the sedation and hurt you.’ It causes a significant drop in blood pressure so should not be used if the horse is bleeding or in shock. This medication can cause the penis to protrude in stallions and geldings, and, in rare cases, causes the penis to prolapse, which can lead to permanent damage if not treated.

As Dowling said, every horse is different and the dose needs to be calculated based on the horse’s weight and other factors, and the person working with the horse needs to be aware that every animal reacts a bit differently. Rarely, a horse may become more agitated rather than calmer.

She added that there are also human drugs that are sometimes used, against veterinary recommendations, although improved drug testing has reduced this. One is fluphenazine, a long-acting sedative that can last for four weeks or longer. “Now you can sell your ‘wingnut’ horse and he doesn’t show his true personality to the new owner for about a month,” Dowling said. Reserpine is another human medication with similar effects. One serious risk to these sedatives, especially fluphenazine is that the horse may ‘freak out,’ according to Dowling, and react by climbing over a stall wall or attempting to escape in other ways that can cause serious injury. This does sometimes happen with acepromazine, but less frequently and less severely.

Herbs have also been used as sedatives or calming agents, although Dowling said, “Most herbal products are safe, but probably minimally effective. Some organizations do ban them, and to do try to test for some of them – valerian, for example. So, be careful depending on what sport you are in.”

Stable owner Marissa Brzescinski agrees that the herbal preparations seem to have little effect. “I’ve found that certain products tend to make the rider more relaxed – much like Dumbo’s magic feather. If they THINK the horse has been given a magic drug to be calm, the riders tend to stay calm, which in turn keeps the horse calmer.”

Dowling finds the best natural products are those containing magnesium, because this element plays a role in nerve impulse transmission. For a consistently hot or anxious horse, feeding extra magnesium in a supplement may be helpful. Overdosing can cause heart problems and diarrhea, however. A higher fat diet is another natural way to calm a horse, compared to a high carbohydrate diet.

Brzescinski feels that sedatives definitely have their place in dealing with horses. “We sedated a horse today to have her hocks injected, and we always sedate for floating,” she said. “I have NO objections to sedating a horse for its own safety or comfort.”

Still, even when there are good reasons for sedation, Dowling advises caution. “Most of these drugs will make the horse ataxic or wobbly, so it’s not always a good idea when you want to work on their hooves. These drugs also interfere with learning, so they are quick fixes, not long-term solutions,” she said.

Avoiding Sedation for Horses

“In situations that involve pain, such as trauma or surgery, of course, sedatives and analgesics are very valuable,” said Dr. Sid Gustafson, a Montana-based veterinarian with a natural approach to equine medicine. “But it’s preferable for horses to be appropriately socialized, taught, desensitized, and prepared to handle most of the situations they’ll be expected to tolerate such as trailering, showing, riding, clipping and medicating.”

Most people would likely prefer to avoid using sedatives or calming medications, but may not be quite sure how to handle horses that become anxious or explosive, or how to train those who are consistently ‘hot’ and can become frustrated.

“Remember that your horse isn’t sitting in his stall planning ways to scare you or get out of doing work,” said University of Guelph professor of Equine Management Katrina Merkies. “Horses are reactionary. They respond to the situation. Sometimes, you get a strong reaction because something scared or hurt the horse in the past, and to the horse this seems like a similar situation. If you can learn to read your horse, your horse will let you know what the problem is.”

It is important to consider that the problem might just be the horse handler or rider. A 2007 study by Uta von Borstel involved 53 horses with their riders. A baseline heart rate when horse and rider were relaxed and comfortable was taken. In one test, the riders guided their horses towards an umbrella that opened and closed, creating anxiety in the horse and in the rider (who was afraid the horse might shy or bolt). The horses’ heart rates were monitored throughout this test. In the other test, the riders were asked to ride in the arena and were told that at some point, von Borstel or her assistants would be unexpectedly squirting the horses with a water gun to startle them. The riders, naturally, became nervous as they anticipated the moment when their mounts would be startled.

Actually, von Borstel never did shoot water at any of the horses. “The horses had no reason to be scared,” she said, “but their heart rates were higher.” In fact, they were as high as in the situation when the scary umbrella was actually present.

The horses in the study were clearly picking up on the anxiety of their riders, and von Borstel noted that any manifestations of this stress in the riders were very subtle. “There were no visible signs of the riders feeling nervous or tense,” she said.

Gustafson said sedatives, while useful in a small number of situations, can too easily be a crutch or a short cut for the horse owner who doesn’t want to put in the time for training. That can be especially true in some competitions. While some equestrian sports are strict about drugs, other are not. Since tests for drugs are not done in some fields of equine competition, or at lower level shows of many sports, it’s impossible to tell with any precision how many horses are actually shown under sedation.

Not only does this make the competition less fair and equitable, but Gustafson said being shown while sedated is potentially hazardous to the horse, and the risks increase the more often the sedatives are used. “Sedatives are a form of sensory deprivation, and they increase the risk of the horse becoming injured,” said Gustafson. “The drug impairs his sensitivity and awareness of what’s going on around him, creating safety issues for both the horse and the people handling him. Sedatives dumb the horse down.” And, while he says a sedated horse may make the top 10, he’s observed that it is the horses who have been trained without medication who win consistently, time after time.

Merkies reminds horse owners that “every time you interact with your horse, you are training. Horses are always reading us, and we are always telling them something. What you want to do is give the horse the sense that he can trust you, that you won’t harm him or let him come to harm, so he knows that he’ll be safe if he does what you ask.”

Tranquilizing medication can actually undermine that sense of trust, Merkies added. “If you tranquilize a horse so you can ride him the first time, for example, it may prevent him from bucking or running off, but the horse now associates being ridden with a weird, fuzzy, out-of-control feeling. He hasn’t truly, totally accepted having a rider, and in fact he has a negative association with the experience. Any problems you have with this horse aren’t really solved, they are only masked.”

If, despite all best efforts to retrain a horse to handle scary situations, he remains uncooperative, Merkies said that though it can be hard to face emotionally, “it might be better for both the rider and the horse to find a new owner for him and a new horse for them.”

Gustafson acknowledges that sedatives have their place, but said they should only be used with caution.”‘Sedatives are an essential part of the vet’s tool kit, but they really shouldn’t be part of a trainer’s tool kit at all,” he said.