Avoid Clostridial Myositis When Administering Banamine
By: Heather Smith Thomas
Veterinarians advise horse owners to give Banamine injections intravenously or orally rather than by intramuscular injection. The worst kind of injection-induced infection is caused by the development of clostridial myositis, and this seems to happen most often when flunixin meglamine (Banamine and generic equivalents) is injected IM.
Clostridial bacteria are always present in the environment. They are often on the horse’s skin and can be taken into the tissues with an injection. These bacteria can be in a dormant state and then multiply when conditions are right; they grow best without oxygen, in bruised/damaged tissue with poor blood supply. The dormant spores “come to life” and start producing deadly toxins. Flunixin meglumine may also set up an ideal pH in the tissues for these bacteria to grow.
Dr. Matt Randall, a veterinarian at Collier Equine in Waller, Texas, says there seems to be more risk with full doses of Banamine, compared to a half dose or less. “To reduce the risk for problems, you can give the product orally. If you can’t get it in the vein, just give a little extra and squirt it in the mouth,” Randall says.
Many people have given IM injections of Banamine for years without problems, but horse owners still need to be aware of the risks. “I have seen three cases and all three horses were very sick and toxic. There is often major swelling at the injection site and gas bubbles under the skin. It feels like Rice Crispies. This warrants an emergency visit to the vet. It can make a big difference in the outcome if you can start treating it early, to reduce the extent of complications.”
The most recent case he’s seen took place when a horse owner called to say her horse colicked two days earlier. “She had some Banamine but couldn’t give it in the vein, so she gave it in the muscle. The next day, her horse was a little stiff-necked and sore at the injection site, so she gave some penicillin, which was fine. By then the mare’s neck was swollen on both sides, she had a fever of 104, and a toxic line on the mucous membranes on her gum,” Randall says.
“I was looking for evidence of gas under the skin as I examined the mare—and found a pocket of gas under the skin by her withers. Gas had traveled along the neck, clear to the withers. I prepped the skin at the injection area, blocked it with anesthesia, and made incisions through the skin and partway down into the muscle,” he says.
An important aspect of treatment is to open the area and get oxygen down into the infection. He made several deep incisions, dissecting down into the muscle. “Suddenly, my finger went into an opening, and I thought maybe I’d been unlucky enough to push into a large blood vessel. I was afraid it might start bleeding, but when I pulled my finger out of the wound, gas rushed out of that hole and the stench was foul. I opened it more, grabbed chunks of necrotic muscle tissue and dragged it out. I opened the infected area, packed it with penicillin-soaked gauze, and started the mare on penicillin injections. Another drug that’s very effective against clostridia is metronidazole,” he explains. This horse also needed a tetanus booster.
“With this mare, I got lucky. She survived, but she ended up with large scars on the side of her neck and some atrophy in those muscles. The most important thing in dealing with this type of infection is getting oxygen into the affected tissues, and that’s why you see photos of horses with large, gaping incisions—for oxygen and drainage,” he says.
“Access to a hyperbaric oxygen chamber would be ideal. This is an excellent treatment modality for clostridial myositis.”
If the injection site and incisions are on the neck, the horse will have a very sore neck; it might be painful to put his head down to eat and drink. “You can help the horse by placing feed and water higher for easier reach. You might not be able to give IV fluids, because of all the infection and gas under the skin. Trying to get into a vein with a catheter would risk a more serious problem,” Randall says.
Mortality rate with this type of infection is fairly high, so it’s important to get your veterinarian involved as soon as possible, to increase the chances of turning the situation around quickly.
