Administering Medications

Author's Note: The purpose of this article is to act as a reference to aid the veterinarian in educating clients in the techniques of medication administration. This article is not intended to act as an encouragement to owner-prescribed medication administration. In fact, I must state that I am personally against an owner making the decision to administer any medications without the advice and direction of a licensed veterinarian. There are many situations where the indiscriminate use of a medication can be harmful, if not deadly. I have seen a number of animals which have been unintentionally harmed by an owner through medication. Also a word of warning to those with human medical training, the action and toxicity of many human drugs can be quite different in horses and other animals, so don't let your training give you a false sense of security when medicating your animals.


Correct way to administer oral medications. Note the position of the dose syringe in the corner of the horse's mouth and over the horse's tongue.

With that said, know that if you can take on the responsibility of proficiently medicating your horses when prescribed by your veterinarian, you often can use a more appropriate therapy and potentially simplify their overall care. But, bear in mind that the responsibility of medication administration should be taken very seriously. With many drugs, the difference between a therapeutic dose and a toxic dose can be relatively narrow--pay attention to numbers, decimal points, and all other details.

Always make sure that the bottles are labeled clearly and that you understand the dose, frequency, and duration of the drug to be administered. Be sure that the prescribed medications are stored separately so that other substances cannot accidentally be administered. Also, if more than one person is going to take responsibility for medication administration, there should be a clear schedule so that double-dosing does not accidentally occur.

If I have a horse on medication, I like to make an administration record for each day (including the time, dose, and place for a check off) and hang it on the stall with a clipboard. Remember: double-check, double-check, double-check.

Now for some math. A common cause of disasters related to medication administration is giving the wrong dose. We must remember that our society stalled out trying to adopt the metric system, and this fact gives many of us difficulty. The common units used for many of the typical medications administered to horses are the milligram (mg) and the milliliter (ml). A liquid drug will generally have a drug concentration reported in milligrams/milliliter (mg/ml). The milligram is 1/1000 of a gram and the milliliter is 1/1000 of a liter. If you want to relate this to non-metric, know that 30.1 grams are equal to 1 ounce, and that 1 liter is equal to 0.946 of a quart.

Another unit that often confuses people is the "CC." The abbreviation "CC" stands for cubic centimeter and is the same unit of volume as a milliliter: 1 ml = 1 cc.

Always follow the prescribed instructions and be very careful. Many drugs come in different strengths, so if you are using an old bottle of something and just draw up the instructed number of CCs, you might be giving an overdose--always double-check the concentrations. Remember, you are playing with your horse's life--if you don't understand how much of a medication to administer, ask your veterinarian.

The most common cause of treatment failure in both human and veterinary medicine is the failure to ensure that the dose is adequate and is administered at the appropriate frequency for the appropriate duration of time. How many half-full prescription bottles are in your medicine cabinet?

Once a course of therapy has been prescribed, it is extremely important that the dose/frequency/duration be followed. As hard as it might be sometimes, there really are important reasons why some drugs are to be given four times per day instead of three. If a horse or your individual situation does not allow for frequent administration of a drug, be sure to point that out to your veterinarian, but keep in mind you might be trading convenience for a less effective drug.

A Word On Drugs

The indiscriminate use of medications can do a great deal of harm, and the administration of medication to your horse should be taken very seriously. I might be a bit hard-line, but I am generally of the opinion that no medications or combinations thereof should be administered to your horse without some form of consultation with your veterinarian. All drugs have the potential to be toxic if used in an indiscriminate manner. There are drugs that can be toxic at the therapeutic doses if predisposing factors exist, and it is necessary to know what side-effects to look for in case there is a reaction. This includes vaccines.

There are many people who are administering vaccinations to their own horses. If you are going to take on this responsibility, you also must take on the responsibility of learning about what can happen if something goes wrong. It might only be one in 100,000 or so horses which have an anaphylactic reaction to a vaccination, but one thing is for certain: If your horse does have one and you don't know what to do, it most likely will die. If you are doing your own vaccinating and de-worming, discuss this with your veterinarian and be prepared to recognize and deal with any complication that might occur.

On the antibiotic front there also are some concerns. The indiscriminate or improper use of antibiotics is a very serious problem in both people and animals. The number of bacteria that are developing resistance to many--if not all--antibiotics is growing at an alarming rate. The emergence of bacteria that are highly resistant to antibiotics is frightening and in many cases related to poor judgment in antibiotic use. If antibiotics are used, we have a high level of responsibility to ensure that 1) the use of antibiotics is really warranted; 2) if antibiotics are warranted, an appropriate one is selected; and 3) if antibiotics are warranted, they are administered by the appropriate route, at the appropriate dose, frequency, and duration.

Oral Administration

There are a number of medications that are formulated to be administered orally in the horse, and many others where tablets or capsules will be crushed or dissolved. A mortar and pestle can aid in the preparation when it is necessary to make a paste out of tablets. One concern is human contact with some medications. When preparing and administering oral medications, care should be taken to avoid contact with the drug--protective gloves work well for this.

Some of the liquid drugs, such as Regumate, are powerful reproductive hormones and are very quickly absorbed through human skin and can cause human illness. Remember to wash your hands. For crushed tablets, I like to mix the drug with some molasses or Karo syrup to a paste-like substance and make the medicine taste a little less evil. Although many horses will have nothing to do with it, there is never any harm done in just seeing if your horse will just eat the prescribed medication out of its grain ration--if not you will need to resort to the dose syringe.

Most of the de-wormers and anti-inflammatory drugs come in "dose-syringes" that have an adjustable wheel on the plunger that is used to set the "based-on-weight" dose. Be very careful, as some of these are not labeled very clearly and the wrong dose easily can be administered. Also, on some products, the little wheel is slightly loose, and if you are struggling with your horse and pushing hard on the plunger, you can inadvertently unload the entire syringe into your horse's mouth!

For the crushed-up, mixed-up medications, your veterinarian will leave you with some form of a dose-syringe. There are many commercial dose syringes available. My preference is the plastic 60 cc syringe with a dose tip. Some of the commercial ones have a long steel nozzle--these must be used with great care because the long steel nozzle can injure the mouth if used roughly or the horse moves its head quickly.

Once your syringe is loaded and you are ready to go, approach your horse slowly and place your hand on top of his nose. Once the horse has relaxed, gently insert the syringe into the corner of his mouth, placing the syringe tip over the middle of his tongue, and unload the contents. Once the contents of the syringe are in his mouth, it is generally necessary to gently hold his head slightly elevated by using the halter or a hand under his jaw until the horse has swallowed--otherwise the precious contents in the syringe will end up on the ground.


Again, this article is meant to re-enforce your veterinarian's instructions for the use of indictable drugs. Direct veterinary consultation and supervision should be obtained before using indictable drugs on your horse.

With that said, one important aspect of giving injections is restraint. Adequate restraint is very important for the safe injection of drugs into your horse's body. You always should have a skilled handler at your horse's head and, depending on your horse's personality, a chain shank and twitch nearby. The handler should be on the same side of the horse as you are--especially when you are working on the hind-end. If the horse goes to kick your lights out and the handler is on the same side, he or she can pull the horse toward you and thus swing the animal's hindquarters (and kick) away from you. Choose the location you are working wisely and make sure you don't get trapped in the stall or squashed between the wall and your horse. Some horses really don't like needles, and concern for your personal safety must be paramount.

The second general concern is hygiene. It must be said that swabbing the skin with alcohol will not sterilize the skin, but it might help reduce or dilute the number of bacteria in the area. If the horse has been out at pasture and is covered in mud or there is a big patch of fecal material stuck to the hair in the area to be injected, it should be washed away with soap and water prior to any injections.

See medication administration images and descriptions here.

Intramuscular (IM)

Vaccinations, antibiotics, and numerous other medications are administered by intramuscular injection. Be very careful only to use medications prescribed (be careful not to accidentally mix up the bottles) by your veterinarian for intramuscular injection as some medications, such as phenylbutazone, can be extremely irritating if injected into the muscle. The general areas selected for intramuscular injection are the neck or the butt, with the butt being preferable. As can be seen by the photos, the upper part of the butt where the large gluteal muscles are located is labeled no and should not be used. The main reason for this is that if the injection site becomes infected (and they do sometimes), that is a very difficult area to drain and treat--it can become a very nasty abscess. The vertical line of white tape, over the hamstring muscles, indicates the zone to be used for intramuscular injection if the hind-end is used. If the injection is made too high near the tip of the upper arrow, the needle might hit the ishchial bone of the pelvis.

In the neck area, a triangle is drawn outlining the ligament near the mane, the front line of the shoulder, and the upper parts of the cervical vertebrae in the neck. A common misconception is the location of the cervical vertebrae in the neck; the horizontal white tape under the triangle on the horse in the photograph shows where the center of the cervical vertebrae in the neck is. The center of the triangle is the thickest and most solid muscle mass in the neck and the selected location for intramuscular injections in the neck.

Your veterinarian might want you to rotate injections from each side of the butt to each side of the neck, depending on the drug being administered, the volume of drug being administered, and the expected duration of treatment. In addition, your horse's personality and willingness to participate might affect the location you are injecting.

The injection technique generally involves inserting the needle with a quick purposeful motion without the syringe attached. This will get the needle in and allow the horse to react without having the syringe dangling. After the horse reacts and calms back down, the syringe can be attached. An extremely important maneuver at this point is to pull back on the plunger of the syringe while observing for the presence of blood being drawn back into the syringe. All of these areas have small blood vessels coursing through, and some dumb luck could place the tip of your needle into one of them. Some of the drugs you could be administering should not be injected into the blood stream (e.g., procaine penicillin). It is very important to pull back on the plunger several times during the administration--especially if the horse moves at all, which can change the location of the needle within the muscle.

Intravenous (IV)

I am reluctant to talk about intravenous injections in any great detail as I feel very strongly that unless you experience significant training and direction, these should be left for a veterinarian or qualified technician. I have several reasons that I'll elaborate on.

The main place for intravenous injection is the jugular vein coursing down either side of the neck. One of the reasons that untrained intravenous injection is dangerous is the proximity of the carotid artery (a little finger size artery that takes blood straight to the brain) to the jugular vein. It's right underneath it! There is not much room for error when giving intravenous injections, and the risk of accidentally injecting a drug into the carotid artery can be great for the inexperienced.

If a drug is inadvertently injected into the carotid artery, the reactions are a little different depending on the drug, but at the very least the horse will flip over backwards and seizure, and, many times, the horse will die. This is the number one reason for leaving intravenous injections to those who are properly trained.

Another reason for staying away from intravenous injections is that some drugs (phenylbutazone being at the top of the list) cannot be administered outside of the vein without causing severe irritation. If you want to see a large portion of your horse's neck slough away, just get some phenylbutazone outside of the vein or accidentally administer it in the muscle. Yet another reason to stay out of the vein is the fact that many drugs cannot be administered into the blood (for example, procaine penicillin) without doing great harm or actually killing the horse.

Should your horse require a drug that only can be given intravenously and your situation will require you to perform these injections, you should discuss this seriously with your veterinarian. You should never attempt this without appropriate training.

If your horse requires the long-term administration of an intravenous antibiotic on the farm, an intravenous catheter can be inserted; the use of a long-term intravenous catheter can decrease the trauma associated with multiple injections and make the medication administration safer. A long-term catheter is a small tube of a rubber-like material (sylastic) that can be inserted into the vein and sutured into place. Drugs then are injected through a rubber portal attached to the end of the catheter, and the catheter is kept clear in-between treatments by the injection of a mild anti-coagulant. These catheters can be fairly easily maintained on the farm and can be left in place for many weeks, if necessary. It is relatively easy to lean how to perform the injections and care for the catheter.

Subcutaneous (SQ)

Occasionally your veterinarian might want a drug to be administered subcutaneously. This means that the drug will be placed just under the skin forming a bleb on top of the muscle. This type of injection typically is performed in the neck area and might be painful, so all of the aforementioned restraint techniques might be necessary.

Ocular Medications

The instillation of ocular medication into the horse's eye can be very difficult. I must again mention the importance of following your veterinarian's instructions as closely as possible. This is an important fact regarding any medication.

As with the injections, restraint and the presence of a good handler can make all the difference in the world. First make sure that all the prescribed medications are in order and that the tubes are clean and dry--sometimes you only get one opportunity, and if the tube slips out of your fingers, it is lost. On the note of fingers, it is a good idea to thoroughly wash your hands prior to performing eye treatments to reduce the risk of contaminating the eye (also be careful not to touch the tip of the eye ointment tube). I also find that it is helpful to wash gently the eyelids and below the eye with a clean gauze patch and warm water. There generally is some residual ointment on the surrounding ocular tissue that will collect dirt and debris near the eye and make the upper eyelid slippery, which can make treatment difficult. Dry the washed skin gently with a clean towel or gauze patch. This whole process also seems to relax many apprehensive horses.

If a twitch needs to be applied to the horse, it is better to do so and get in and get out with the treatment rather than fighting with the horse. The best technique I have found for the application of ocular ointments is to place the index finger on the upper eyelid and the thumb at the edge of the lower eyelid. When the lower eyelid is pulled down on, it is slightly everted and the prescribed quantity (usually something like a "half-inch strip of the ointment) can be placed just inside the edge of the lower eyelid. It is very important not to let the tip of the metal tube come into contact with the surface of the eye. If the hand holding the tube is kept in contact with the head, the chances of gouging the eye with the ointment tube will be reduced because if the horse throws its head, your hand and the tube will move with the horse's head. The application of drops is a whole new challenge. You must have the handler try to tilt the horse's head at about a 45-degree angle, then hold the lids open and apply the drops--without touching the eye!

Again, if your situation requires you to administer medication yourself, make sure your veterinarian explains administration thoroughly. Don't be afraid to ask him or her to go over the procedure several times and demonstrate with the first dose. Remember, the number one cause of treatment failure in both veterinary and human medicine is owner or patient non-compliance with respect to following prescription directions (dose, frequency, and duration). It is a simple fact that the harder it is to do the treatment, the more likely it is for the treatments to be inadequate or skipped.

About the Author

Michael Ball, DVM

Michael A. Ball, DVM, completed an internship in medicine and surgery and an internship in anesthesia at the University of Georgia in 1994, a residency in internal medicine, and graduate work in pharmacology at Cornell University in 1997, and was on staff at Cornell before starting Early Winter Equine Medicine & Surgery located in Ithaca, N.Y. He is also an FEI veterinarian and works internationally with the United States Equestrian Team.

Ball authored Understanding The Equine Eye, Understanding Basic Horse Care, and Understanding Equine First Aid, published by Eclipse Press and available at or by calling 800/582-5604.

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