We routinely sedate horses in practice – after vaccination, it’s probably the most common “routine” job that we do. How do the drugs work – and why doesn’t it always happen the same way? produced by a sedative drug.” That’s the dictionary definition, and it makes it sound lovely and simple – give a drug, and the patient goes to sleep.
Of course, in reality (as usual with anything equine! For those who haven’t seen it before, a sedated horse doesn’t lie down, but their head gets lower and lower, and they may require something to lean on to help them balance.
Generally, it’s to make the horse more amenable when something nasty or scary is being done to them. There are quite a lot of horses out there that need a sedative before the farrier can trim their feet; and there are others that will allow you to suture up a wound without sedation or even local anaesthetic (not recommended, but occasionally necessary).
The drug usually used is butorphanol, which is a synthetic opiate (it’s a mu/kappa agonist/antagonist related to buprenorphine, for anyone interested) that has a fairly good painkilling effect as well as potentiating sedation from other drugs.
Fortunately, it also has very few side effects, although its worth bearing in mind that any other opiates (e.g.
Pethidine or Fentanyl) that the horse is given up to about 8 hours later won’t work quite like they’re supposed to, as the butorphanol will partially block their activity.
Firstly, it can lead to significant drop in blood pressure, because it makes peripheral blood vessels dilate (this is why it’s sometimes used in laminitis).
The second effect is much more interesting – ACP is a mild muscle relacant of some muscle types, so it can be useful in azoturia and choke.
A quick note on ACP tablets – under the current Veterinary Medicines Cascade laws, it is illegal to use ACP tablets instead of paste in horses unless the vet has a clinical reason (unfortunately, price isn’t considered good enough) to think that they are more appropriate.