Non-steroidal anti-inflammatory drugs help treat the root cause of laminitis
Laminitis (founder) – or inflammation and degeneration of the laminae in a horse’s foot – is unique to horses and other hoof stock. There are a number of reasons why the disease can occur and cases vary in severity. All cases involve inflammation, which makes the disease a prime target for treatment with non-steroidal anti-inflammatory drugs (NSAIDs).
Even with a long history of battling the disease, treatments and success are varied.
“The ancient Greeks knew about laminitis, and we still don’t understand the whole disease,” says Earl M. Gaughan, DVM, Dipl. ACVS, technical services veterinarian with Merck Animal Health. “There are a number of ways a horse can founder. When a horse has substantial problems with nutrition, damage can occur to the laminae inside the hoof that makes it difficult to support the weight of the horse. Then, the tissues can experience physical break down.”
In cases of laminitis, the horse’s tissues – or laminae – that connect the hoof wall to bone become inflamed. This weakens the bond between the bone and hoof and results in lameness.
There are three major reasons why an NSAID is helpful in treating laminitis, Dr. Gaughan says. First, the inflammation in the hoof can reduce blood flow, which further contributes to laminitis progression. Second, the condition is painful for the animal. Finally, endotoxins can be released from bacteria in the intestinal tract, which can contribute to laminitis, and some NSAIDs can help retard the release of these endotoxins.
The flip side
Other possible treatments have included dimethyl sulfoxide (DMSO), anti-coagulants, ice baths, and physical support like supportive bedding or shoeing. Veterinarians choose their tactics to increase blood flow to the foot and support the physical weight of the horse.
Every treatment has risks, and drugs often used to treat laminitis are no different. Horses should be monitored closely to ensure they continue to eat and drink normally, Dr. Gaughan recommends.
“Some of these drugs can have negative effects,” he says. “You want to stabilize horses systemically, especially where it concerns the cardiovascular system. These are not drugs where if a little is good, a lot is better. This is one area where I would almost refer to the treatment of laminitis as an art form. There’s not a set formula. We need to pause and make sure we look at the whole horse and not just the feet. We’re trying to stop the process and prevent irreversible changes from happening.”
To help prevent negative effects from the treatment itself, Dr. Gaughan says medication is prescribed at the appropriate dose for the shortest period of time required. If there is a typical laminitis case, treatment can be between one and four weeks.
Signs of NSAID toxicity can include a horse going off feed or water, a depressed mental attitude, colic, loose stool or diarrhea.
Selecting an NSAID
Most NSAIDs used today are non-selective cyclooxygenase (COX) inhibitors, which block both an animal’s enzymes for producing pain and inflammation as well as the beneficial enzymes that promote blood flow to the tissues and protective the mucous lining in the stomach and colon, says P.O. Eric Mueller, DVM, PhD, Dipl. ACVM, chief medical officer – large animal hospital and director of equine programs at the University of Georgia.
“All these NSAIDs are really good drugs, but most have a very low margin of safety,” Dr. Mueller says. “The right dosage for the right amount of time is very helpful, but if you give twice the dosage for a very short time, you can run into complications.”
With most NSAIDs used in laminitis treatment today, those side effects can include going off feed, ulcers in the right dorsal colon and stomach, and kidney disease.
“The initial problem is an inflammation of laminae that leads to instability between the bone and hoof in the foot,” he says. “While the horse is in that early phase, we try to preserve the alignment of the foot within the hoof capsule by minimizing inflammation and supporting the foot as best you can. NSAIDs can help minimize inflammation.”
In addition, pain relievers should help ease the horse’s distress, but not encourage too much movement that could contribute to further instability and progression of the disease.
Horses that are eating and drinking normally likely won’t have a negative reaction to NSAID therapy at appropriate dosages, Dr. Mueller says. However, veterinarians will keep a close eye out for signs of NSAID toxicity such as going off feed, diarrhea and kidney disease.
Duration of NSAID treatment is also a concern. A mild case of laminitis may respond to 24 to 48 hours of treatment and 30 to 45 days of restricted activity.
“The longer the horses are on NSAIDs, and the higher the dose, the more likely they are going to have problems,” Dr. Mueller says.
Anything above two grams of phenylbutazone, two times a day, for three or four days for a 1,000-pound horse could cause serious side-effects, he says. In addition, younger and older horses (22 to 25 years old) are at a higher risk for NSAID toxicity.
“The bottom line is we try to effectively treat laminitis with the least amount of medication and optimal foot support to provide the best result,” Dr. Mueller says. “It’s always a combination of different therapeutic agents and supportive care. Laminitis has had many different treatments tried over the years, none of which are 100 percent effective. The ones that seem to be the most reliable are NSAIDs, DMSO, ice baths and supportive care.”
• Common NSAIDs used in laminitis treatment: firocoxib, flunixin meglumine and phenylbutazone
• Risk factors for laminitis include: diet or dietary changes, toxins or gastrointestinal disease.1
• Horses eating excessive amounts of grain are more likely to have laminitis.1
• Excessive weight bearing on one limb puts the overloaded limb at higher risk for laminitis.1
1 White NA and DuPont M. Equine laminitis. Virginia-Maryland Regional College of Veterinary Medicine at Virginia Tech.