Yes, I am a trainer’s wife but there are a couple of things down at the barn that I loathe. One of the them is hooking up a trailer. And the second is giving a penicillin shot. Penicillin is a potent, antibiotic often used in horses against a variety of pathogenic organisms. I figure my reason for hating these sometimes necessary tasks is because any mistake I make in doing either, would likely result in the death of an animal. A trailer that comes unhooked on the highway is dangerous to me, other drivers and the precious cargo I have in the back. A penicillin shot gone wrong can be potentially and immediately fatal for my horse. For that reason, I decided to research some little known facts about the drug and helpful tips for administering penicillin:
• I’m sure I don’t need to tell you that you must always ensure you give penicillin shot with a sterile needle and syringe, (never reuse a needle because a contaminated needle can easily introduce an infection into a horse.) But it may be helpful to know that 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) is good for thin, watery solutions.
• 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.
• Penicillin is very commonly administered to horses in a formulation known as penicillin procain G. The procaine is a local anesthetic which is related to lidocaine, novacaine and believe it or not, cocaine.
• When administered properly, penicillin usually does not result in a problem. But care must be to ensure procaine penicillin is always injected intramuscularly. If it is administered into IV or into a vein, it can be dangerous and potentially fatal for your horse. If the drug is accidentally injected into the horse’s bloodstream, the procaine goes directly to the horse’s brain and causes the animal to tremble violently and throw itself over backwards. There is no antidote for this reaction and it is not only dangerous to the horse, it is extremely dangerous for bystanders. For that reason, after you have inserted the needle into a designated injection site, you must pull back on the syringe plunger a bit to make sure there is no blood in the syringe. (Or if you prefer to put the needle in first and secondly, attach the syringe filled with medicine, watch the hub of the needle to see if it fills with blood. If blood is present, remove the needle and start over. Never follow through with the injection if you see blood! When you can pull back on the plunger and no blood appears, it’s safe to inject the penicillin into your horse.
• Penicillin also has the ability to trigger allergic or anaphylactic reactions in certain animals that can occur unpredictably with varying intensity. Should this happen, discontinue use of the penicillin and call a veterinarian immediately. Allergic reactions typically require previous exposure to the drug and then the problem is manefested by hives and head swelling. Occasionally, it can also result in massive constriction of the airwaves and sudden death.
As there are many great antibiotics are available to your veterinarian these days, it’s possible penicillin may not be prescribed in unfortunate circumstances that affect your horse’s well being. But if it is, just remember that procaine penicillin G is a very beneficial drug to use in the war against wound infections, secondary bacterial infections in respiratory diseases, and various other injuries or diseases. Always consult with your veterinarian before administering a penicillin regime so you clearly understand this drug’s proper dosages, frequency of administration and withdrawal times.