Learn how to correctly administer medications via needle with Amy Armentrout, DVM.

If you spend any amount of time caring for horses you’ll probably have to administer medication as some point. While giving a horse medication orally can be easier on the handler, not all medications are effective when given this way. It’s important to learn the right way to give your horse medication by injection. Amy Armentrout, DVM, shares important directions for correctly and safely giving your horse medication by needle.

Why Injections—in the Right Location—Are Necessary

Medication administration recommendations are made based on how the medication is metabolized by the horse.

“Some medications, like penicillin, are not absorbed orally or in the gastrointestinal tract, so they must be given by injection,” Armentrout said.

However, not all injections should be given in the same method. Some, like procaine penicillin G—the common form of penicillin found in many farm stores—cannot be given intravenously. It must be given intramuscularly. Others, like Banamine, should be given intravenously or orally, because it is irritating in the muscle, Armentrout says.

“Never inject anything in your horse unless you are fully aware of the potential side effects of the medication,” Armentrout said. “Work with your veterinarian to learn about the medications you commonly use.”

Decoding the Methods

Subcutaneous injections are a common method for giving an injection to dogs but are rarely performed in horses, so they won’t be discussed in this article.

“The most common routes of administration of injectable medications are intramuscular (IM) and intravenous (IV),” Armentrout said.

As mentioned, Banamine can be given orally or intravenously. Dexamethasone can be given orally, intramuscularly and intravenously. Procaine Penicillin G can only be given intramuscularly. Injectable phenylbutazone can only be given intravenously

Safety First

Reusing needles and syringes is dangerous. They can harbor bacteria and lead to infections—some may be minor and can be treated with antibiotics, others can be potentially life-threatening, like Clostridial myositis.

Any medication given in the muscle has the potential to cause swelling, pain or fever. Visit with your veterinarian about potential side effects for any medication so you are educated about what’s normal after administration.

Contact your veterinarian if you notice any of these signs to determine if they’re a cause for concern.

If your horse has a history of reacting to an injection, it’s probably better to have a veterinarian administer future injections.

“You should avoid injecting horses for friends,” Armentrout said. “If the horse has an adverse reaction, you could be liable.”

Intravenous injections can be dangerous, Armentrout says. The carotid artery is separated from the jugular vein by a muscle called the omohyoideous muscle. It is thicker in the upper third of the neck and gets thinner as it goes down the neck. That’s why injecting in the upper one-third of the neck is safer.

Intramuscular Injections
Prepare

  1. First, ensure the horse is being held by a competent handler who is standing on the same side as the injection will be given. Do not have the horse tied up.
  2. Make sure the environment is calm and quiet.
  3. Ensure that the injection site is relatively clean.
  4. Use a freshly opened, new needle and syringe for every injection. Never reuse needles or syringes.
  5. Make sure you are about to administer: The correct drug; The correct amount, or dose, of that drug; The correct route—is this medication definitely supposed to be administered IM?; That you’re giving it at the correct time of day.

Injection Site

Select a location for injection. These usually include the neck or semimembranosus/ tendinosis—the haunches—on the left or right side. Try to alternate between locations, especially if you’re injecting a large volume, i.e. greater than 10 millileters.

“We generally recommend people use a system to remember rotating,” Armentrout said. “Such as ‘give it in the right at night’ if it’s a medication given twice daily.”

Armentrout shows where to give horses injections in the neck.
For an intramuscular injection, inject in the triangular space between the scapula at the base of the neck, the cervical spine at the bottom of the neck, and the nuchal ligament at the top of the neck. The area is wetted down in this photo. Photo by Abigail Boatwright.

The Neck
Look for these landmarks when injecting in the neck muscle:

  • The scapula (shoulder blade)—at the base of the neck
  • The cervical spine (neck vertebrae)—at the bottom of the neck
  • The nuchal ligament—at the top of the neck.

You should inject in the triangle approximately a hand’s width in front of the shoulder blade, about halfway between the nuchal ligament and cervical vertebrae. If you’re not sure how to find this, ask your veterinarian to show you in person.

The Haunches (semimembranosus/tendinosis muscles)

Where to give injections in the haunches.
To give an intramuscular injection in the haunches, aim for the large muscles, below the bone you can feel alongside the tail. The area is wetted down in this photo. Photo by Abigail Boatwright.

The aim is to inject into the large muscle mass of the haunches, Armentrout says. You want to feel for the bony prominence of the tuber sacrale, the bone that you can palpate alongside the tail. You will inject below the tuber sacrale, alongside the tail.

“Only inject in this area if the horse is of suitable temperament for you to do so safely,” Armentrout said.

Pectoral Muscles

Pectoral muscles are occasionally used as an injection site, but they generally swell after injection, so Armentrout recommends choosing one of the other sites.

Gluteals

Armentrout does not recommend injecting in the gluteals, because if an infection develops in an injection site, it will not drain well in this area.

IM Injection Technique

  1. Select the appropriate site for your injection.
  2. Make sure the injection site is clean and free from debris stuck in the hair, like mud and manure.
  3. Stand in an appropriate and safe position, in case the horse reacts to the needle being inserted.
  4. Quickly and decisively, insert the needle perpendicular to the skin. A fast stab is less painful for the horse. The entire length of the needle, up to the hub, should be inserted into the muscle.
  5. Attach your syringe to the needle and pull back on the plunger, drawing it back to check for blood. If blood is seen in the syringe: Detach your syringe; Pull needle halfway out; Change direction of the needle by a few degrees; Re-insert needle; Re-attach syringe; Draw back again to check there’s no blood: 1) If no blood is seen, inject the medication slowly, over a few seconds. 2) Once the syringe is empty, the needle and syringe should be removed together in one smooth movement.

In general, 1 ½ inch needles should be used, and 18-20 gauge, depending on the thickness of the medication.

Armentrout shows how to give horses injections intramuscularly.
For an intramuscular injection, insert the needle perpendicular to the skin. Pull back the plunger to check for blood—for an intramuscular injection, there should be none. Then inject the medication slowly. Photos by Abigail Boatwright.

Intravenous Injection

This type of injection is done in the upper one-third of the horse’s neck. The jugular vein is superficial in the jugular furrow.

  1. Find the jugular vein. You can do this by holding the horse’s head up without turning it to the left or right. You want to focus on the first one-third of the horse’s neck, closer to its head. Avoid injecting lower down the neck.
  2. Wet the horse’s neck with alcohol. This will make finding the vein easier, as well as cleaning the site.
  3. Hold the vein off for a prolonged period of time, about 3-4 inches lower than the area you plan on using for the injection. The heart beats slowly, and it takes a while for the vein to fill.
  4. Look at the needle, and make sure that the beveled edge is facing you when you inject the horse. If the edge is facing the horse, this will make puncture more difficult, and can affect the release of the medication.
  5. Place the needle in the vein with no syringe attached to the needle. Don’t prick the horse repeatedly. If blood drips out, you are mostly likely in the vein. If blood streams out under pressure, or pulses, you are in the artery and should remove the needle immediately. Medication in the artery will cause seizures and can have more serious consequences, such as permanent blindness and death.
  6. Once the tip of the needle is in the vein, adjust the angle of entry to be parallel to the vein—not perpendicular—and then press the needle into the horse until all you can see is the hub. This prevents an incorrect administration of the medication or the needle coming out too soon. This will also help avoid accidentally entering an artery by using too great an angle. As a helpful tip, since the vein is so shallow under the skin, you can usually feel the needle in the vein through the skin.
Armentrout shows how to give horses injections intravenously.
For an intravenous injection, first locate the jugular vein. Wet the neck with alcohol, then hold the vein so it can fill. Lining the needle up parallel to the vein, insert needle into the vein. Photos by Abigail Boatwright.
Armentrout shows how to check for blood when giving injections intravenously.
Look for blood—with an intravenous injection, the syringe should fill. If blood is streaming out or pulsing, you have hit an artery and you need to remove the needle and try again. Insert needle fully, and inject the medication. Photos by Abigail Boatwright.
Armentrout shows how to give horses injections intravenously.
Note: While learning to inject intravenously, Armentrout recommends pointing the needle down the vein and placing it unattached to the syringe while still holding off the vein below. Then, attach the syringe and pull blood back to check your placement. Photos by Abigail Boatwright.

Avoid:

  • Incorrect location
  • “Stick and fish” technique. Carefully assess your location and then commit to placing the needle. Don’t pull the needle out if you haven’t found the vein. Try rotating the needle to open up the bevel edge.
  • Incorrect bevel orientation
  • Too short of a needle
  • Placing only the tip of the needle in the vein
  • Changing your hand position while placing, aspirating and injecting. Once you are experienced with injecting in the vein, you can point the end of the needle toward the head like you commonly see your veterinarian do when performing injections. When you are learning, Armentrout recommends pointing the needle down the vein and placing it unattached to the syringe while you continue to hold off the vein below it. It will be easier to tell that you are in the artery if blood sprays out of the needle under pressure. If this happens, remove your needle and move higher up the horse’s neck toward the neck to choose a new location for injection.

You can then carefully attach your syringe, without moving your needle, and pull blood back into the syringe to check placement. You can work with your veterinarian to learn to properly access a vein.

“Remember, intravenous injections are not without risk,” Armentrout said. “If the horse begins shaking their head or rolling their eyes, stop injecting immediately and clear the area in case the horse starts to have a seizure from injection in the artery. Additionally, there are medications that can be irritating to the neck if they get outside of the vein. They can cause serious problems, like forming an abscess or forming a large clot in the jugular vein that can cause the horse to lose the jugular vein (thrombophlebitis or complete thrombosis). This can affect drainage from the head, causing temporary head swelling and can have performance issues if left untreated.”

If you aren’t confident injecting intravenously, ask your veterinarian to show you how before you take the medicine home to inject your horse on your own.

This article was originally published in the May 2019 issue of Barrel Horse News.

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