ANR-1018, New Dec 1996. Cynthia A. McCall, Extension Animal Scientist, Associate Professor, Animal and Dairy Sciences, Auburn University
Most horse owners occasionally must give their horse an injection. Fortunately, giving an injection to a horse is an easily learned skill. Determining what type of medication the horse needs and how to administer the medication is the critical part of the process and should be determined by your veterinarian.
Intramuscular injections are the most common type used in horses and are the focus of this article. Although a few horses are needle shy and object to injections, most horses quietly accept a properly given IM injection. By following the methods outlined, horse owners should be able to safely and efficiently give an IM injection to a horse.
Although giving an IM injection to the horse is a routine procedure, it is not without risk to the horse. Always consult your veterinarian about the type of medication, the dosage and the route (intramuscular, intravenous, subcutaneous, or intradermal) before giving any drug to a horse.
Improper drug handling and injection techniques can result in infections and life-threatening drug reactions as well as rendering the drugs or vaccines ineffective. Have your veterinarian discuss signs of drug reaction in the horse and how to handle this situation.
Giving an injection to a horse also can pose some risk to the human handler. If at all possible, have two people available when giving an injection. One person holds the horse while the other person gives the injection. A horse that seriously objects to the injection can easily injure the handler as well as itself. Also, some drugs used in horses can be absorbed directly through human skin or can produce severe reactions if accidentally injected into humans by needle punctures.
Make sure to ask your veterinarian about any safety precautions you should take when handling a drug or giving an injection.
Before giving any injection, read the drug label on the bottle. It is a good practice to check the label before you draw the medication out of the bottle and again before you inject the drug into the horse. Check the drug name to ensure it is the one recommended by your veterinarian. Remember, the generic name for a drug and the brand name may differ.
Next check the recommended dosage. This may differ from the instructions given by your veterinarian. If you have any questions about the dosage, get clarification from your veterinarian.
Check the recommended route of injecting the drug. Again, if you have questions, check with your veterinarian.
Follow the recommended method of drug storage, drug handling procedures, expiration date and precautions. Do not mix individually packaged drugs in the same injection. Compounds in one drug preparation may inactivate or decrease the efficacy of the other drug. It is better to play it safe and give the horse two separate injections.
Next, make sure you use a sterile needle and syringe. Individually packaged, disposable sterile needles and syringes are the easiest way to ensure sterile equipment. Open the packages immediately before use and dispose of them immediately after use, preferably in an approved medical waste container. Never reuse a needle because a contaminated needle can easily introduce an infection into a horse and do not use the same needle or syringe on more than one horse.
The size of the needle depends on the medication being injected. A large-diameter needle (18 gauge) works best with thick solutions such as penicillin, while a smaller-diameter needle (20 to 21 gauge) can handle a thin, watery solution. Remember, a larger gauge number equals a smaller diameter. Larger gauge needles may break more easily than smaller gauge. If your horse reacts adversely to the injection and breaks the needle, you should make sure you can find both pieces of the needle. If you suspect a piece of needle may be retained in the horse's muscle, consult your veterinarian.
Most IM shots are given to adult horses with a 1 1/2-inch needle so that the medication is injected deep into the muscle mass. Foals are usually given IM injections with a 1-inch needle. Collect used needles, with their plastic covers attached, and syringes in a resealable plastic bag or bottle and take them to your veterinarian's office for disposal in an approved medical waste container.
Antiseptic cleansing of the injection site is not commonly practiced by most horse owners or veterinarians. They simply brush any noticeable dirt from the injection area and insert the needle into dry skin. There is no noticeable increase in infection with this method when compared with a method that uses an antiseptic cleansing agent.
Studies have shown that swabbing the area with an antiseptic has very little effect on the cleanliness of the injection site. To thoroughly clean the injection site, the horse's hair must be shaved, the area scrubbed with an antiseptic soap which must remain in contact with the skin for at least two minutes,then rinsed with alcohol. This is impractical for most horse owners and most people do not want their horse shaved at the injection site. Using a sterile needle and syringe is more important in preventing injection site infections than thoroughly cleaning the site.
When injecting a horse, you can never be sure how your horse will react; therefore, it is best to untie the horse and hold its lead line or have someone else hold it. A tied horse that overreacts to the injection may pull back against the tie rope. The resulting pressure on the horse's head may cause it to panic, injuring the horse or the handler. If the horse does pull back during the injection, simply move with the horse and continue the injection when it calms down. If the horse tries to kick, pull its head toward you. This automatically swings its rear end away from you. Some seriously needle-shy horses may need to be distracted by a twitch (a restraint device that tightly grips the horse's upper lip and nose) or the chain end of a stallion lead run through the mouth or over the upper gum. For horses that are extremely dangerous to inject, another option for the experienced horseman is tying or placing a horse in stock. You could also consult your veterinarian about this method.
The site of the IM injection is important for the safety of the horse and the handler. Choose a large muscle mass that is actively used by the horse. This promotes drug absorption and decreases the chance of swelling and pain at the injection site. The site should allow the needle to be placed deep in the muscle without danger of hitting bone, ligaments, nerves or blood vessels. Also, the injection site should allow the handler to be in a relatively safe position if the horse objects to the injection.
The base of the horse's neck is an injection site favored by many horse handlers because it allows the handler to remain in a relatively safe area by the horse's shoulder.
This site is a triangle defined by the nuchal ligaments along the crest of the horse's neck, the cervical vertebrae that form a backward S-shaped curve from between the horse's ears toward the point of the shoulder, and the scapula. (see Figure 1).
To locate the appropriate injection area, put the heel of your hand on the base of the horse's neck where it joins the shoulder, about midway between the crest and the bottom of the neck. The area covered by your palm is the injection site.
Higher toward the crest, you risk hitting the nuchal ligaments, and lower toward the bottom of the neck is where the cervical vertebrae and blood vessels are located. Make sure you stay near the base of the neck rather than injecting higher up the neck toward the ears. This again avoids ligaments, bone and blood vessels and gives a larger muscle mass for the injection.
Remember to never give a nursing foal an injection in the neck. If the neck becomes sore from the injection, the foal may be reluctant to nurse.
Below the point of the horse's buttocks is another large muscle mass (semitendinosus) that is a good injection site (see Figure 2). Because this muscle is used every time the horse takes a step, it is a good site for drugs that might cause swelling and pain at the injection site. It is the preferred injection site in foals because it is one of the larger muscles on a foal's body.
The major drawback to this injection site is that it puts the handler within kicking range of the horse and should be used only by experienced horse handlers. Horse handlers should remember that horses may kick at the person inflicting pain rather than at the painful area. You are not safe from being kicked if you stand on the left side of the horse and reach across the horse to inject its right buttock. The horse may kick at you with its left hind leg rather than kick at the site of the injection with its right hind leg.
To find this injection site, simply locate the bony protrusion that makes up the point of the buttocks (tuber ischii). Drop about 1 inch below the tuber ischii and inject anywhere in the large muscle mass along the back of the leg.
The pectoral muscles in the chest are another possible injection site (see Figure 3). This site does put the handler at some risk because the handler must lean over in front of the horse to see the site clearly, putting him in a position where he could be easily bitten, struck with a front foot or run over by the horse. The pectoral muscles tend to become sore easily and generally are only used when the horse is receiving prolonged treatment and is sore in other injection sites. However, if a problem occurs, this area drains very well.
This injection site is the bunchy muscles in the lower half of the chest between the tops of the forelegs.
Many horse handlers use the top of the rump (gluteal muscles) as an injection site. This is a large, frequently used muscle mass which allows the handler to stand in a relatively safe area while giving the injection.
The disadvantage to this site is that it has very poor drainage if a needle abscess develops. An infection at this site tends to spread up the loin and back and cannot be treated easily. Therefore, it is not a recommended injection site. However, it can be used as a last resort for a difficult horse or a horse that is sore in all other injection sites.
The proper location of this site is the intersection of a line between the tail head and point of hip and a line between the top of the croup and the point of the buttocks.
Novice horse owners often worry about injecting air into the horse when the needle is inserted without the syringe attached. However, this amount of air injected into the horse is minor and will not harm it.
A quiet horse may allow you to simply pop the needle into its neck or buttocks. However, if the horse needs a little distraction, there are several methods of easing the needle stick. One good method is to pinch up the horse's skin next to the injection site for a few seconds prior to inserting the needle (see Figure 5). While holding the pinched skin, insert the needle next to the pinched area.
Another method is to hold the needle between the thumb and forefinger. Tap the horse vigorously two or three times with the side of your palm in the injection site, and without breaking your rhythm, rotate your hand and insert the needle (see Figure 6). However, some horses may learn to associate the taps with the following needle stick and leave the area prior to the needle stick. Also, if used for injections in the neck, the tapping technique may promote a horse to be more reactive to hand movement around the head and neck area.
A similar method is rubbing against the direction of horse's hair growth several times while holding the needle between the thumb and forefinger. Insert the needle on the last rub.
Giving your horse an IM injection is an easily learned technique. By observing proper safety rules and injection techniques, you can often avoid infections and adverse drug reactions. A summary of the IM injection procedure follows.