Instructions
You'll need a 1 1/2-inch-long needle and a 20-gauge syringe. Unwrap the needle and syringe, and place the needle on the syringe. Insert the needle into the rubber top of the Acepromazine bottle. Slowly pull the syringe's plunger back to draw the Ace out of the bottle. Use the measurement marks on the side to determine how much is in the syringe. For minor procedures, use 0.5 to 1 milligrams per 100 pounds of weight. (A vet may recommend 2 to 4 milligrams per pound for medical procedures.) It is better to start out with a lower dose if your horse has not had Ace before or if you do not know how it will react.
Hold the syringe upright so the needle is pointing up. Tap the side of the syringe to break any bubbles. Slowly depress the plunger while it is upright to remove any air from the syringe. The air is gone when the Ace reaches the head of the needle and starts to come out. Check the amount of Ace in the syringe again. Put the cover on the needle to protect it.
Restrain your horse by tying it or having someone hold it. You should always have someone assist you if you don't know how your horse will react.
Choose an injection site. Intramuscular injections can be given in the neck, buttocks, top of the rump or pectoral muscles. The easiest and safest site is the neck. This allows the horse to hear and see you and will keep you out of reach of its hooves if it decides to kick or jump to the side. There is a triangle of muscles at the base of the horse' neck (above the shoulder) where the injection should be given.
Remove the needle from the syringe and the cover from the needle. Hold the needle between your thumb and first two fingers. With the back of your hand, stroke the horse on the neck and gently pat it near the injection site. This will help desensitize it to your contact in this area. In one quick motion, pat the neck and then insert the needle fully into the muscle.
Attach the syringe to the needle and pull the plunger back (out). You should not see blood in the syringe. If you suck blood into the syringe, you must remove the needle and try again. If the syringe is free of blood, depress the plunger and give the horse the injection.
Wait 30 to 60 minutes for the Ace to start working.
How to Give a Horse Acepromazine
According to the Wedgewood Pharmacy website, Acepromazine is one of the tranquilizers most commonly used in horses. Acepromazine, or "Ace," causes muscle relaxation and is used to calm a horse during minor medical procedures. Some owners also use Ace for procedures like clipping a horse's hair or transporting a horse. Ace can be given intravenously (into a vein) or intramuscularly (into a muscle), but most horse owners inject the drug into the muscle. Intravenous medication is best left to veterinarians.