PROCEDURE
Prepare the medication and have it ready to administer. Halter your horse. Starting on the horse’s right side, and facing your horse's right eye, grasp the halter with the left hand but do not apply pressure unless your horse moves its head.
Put your right hand against the right side of the horse's muzzle and spend a second with it there. Now insert your thumb in the corner of the horse’s mouth. Most horses will open their mouths easily. Be careful not to get your thumb too far back, as the molar teeth start about 3 centimeters behind the corner of the mouth, and you can be severely bitten.
When the horse opens its mouth easily for your fingers, without resistance or pulling back, you are ready to insert the syringe. Place the syringe in the corner of your horse’s mouth and back onto the tongue base and depress the plunger, squirting the medication into the mouth, and remove the syringe.
If you are concerned that the horse will spit the medication out, push your left thumb into the roof of the mouth to stimulate chewing, which spreads the medication in the mouth, making it harder to spit out. Reward the horse with release, and a kind word or a rub on the head.
TIPS FOR SAFETY AND SUCCESS
If you cannot get your thumb easily into your horse's mouth without them tolerating it well, you may not be able to give them oral medication with ease. In this case, or if your horse resists in other ways, you may want to review the related skill, Give Oral Medication to a Difficult Horse.
Some medications may need to be crushed while others may dissolve rapidly. Ask your vet what the best method is for the particular medication being used.
Give oral medications prior to feeding your horse. Once a horse has a mouthful of feed, it is easier for them to spit out the medication with a wad of feed.
If the medication is particularly bitter or you believe that the horse dislikes the taste, you can mix some Caro Syrup or molasses with the medication. Make sure your horse's mouth is empty, and that there is not a wad of feed in your horse's mouth. After giving your horse the oral medicine, you can immediately give them a dose of corn syrup, molasses or apple sauce to end on a positive note.