Colic's Under Attack at North Carolina State

Would you take ibuprofen for a stomachache? Your doctor likely wouldn't recommend it; heartburn, stomach cramps, and nausea are known "common side effects." But dosing with non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen--phenylbutazone (Bute) or flunixin meglumine (Banamine)--is exactly what we do with colicking horses. Add that to the recently recognized fact that Banamine slows down repair of the equine gut, and treating colic with NSAIDs doesn't seem to make a lot of sense.

Many researchers are trying to find better medications for treating colic. North Carolina State University's Anthony Blikslager, DVM, PhD, Dipl. ACVS, interim department head and associate professor of equine surgery, and Sam Jones, DVM, PhD, Dipl. ACVIM, associate professor of equine medicine, are helping lead that charge.

Healing Equine Intestine

"What seems to make horses recover more rapidly is something they produce all by themselves--prostaglandin," says Blikslager. "If you give a horse synthetic prostaglandin, it will make his gut repair faster. But prostaglandin is what NSAIDs block, which is why they slow down healing. When you injure the body, it will produce more prostaglandins. So if you just let it do that by not using a drug that completely shuts down their production, it will take care of itself.

"If you just looked at the gut itself, it would repair much better if it was left alone," he adds. "But you can't really do that, because they're sick and in pain, so we have to do something. So we pick the most appropriate medications for pain, combating shock, etc. I think there ultimately will be better medications for that than what we've got right now."

Researching Colic Medications

"Our long-term goals are to understand how inflammation damages intestinal tissues and causes the systemic effects of sepsis, and find out what we can do therapeutically," says Jones.

Inflammation starts with a trigger (such as endotoxin from an altered gut bacterial population due to carbohydrate overload). That trigger initiates a cascade of chemical signaling that stimulates cells to produce prostaglandins or do any of a number of actions. Jones' work focuses on the following topics:

  • Map out the pathways in the horse whereby inflammation is activated and prostaglandins are produced.
  • Find out where those pathways can be interrupted to help heal the gut without compromising other tissues.

Lidocaine, a local anesthetic, "also appears to help horses with postoperative ileus (accumulation of fluid in a dysfunctional bowel)," says Blikslager. "One possible way it works is that it blocks nerves that feed into the gut and slow it down. The other is that it's an anti-inflammatory all by itself--it has an effect on white.blood cells, which nobody ever imagined when they first started giving it.

"We give it systemically--you start with a bolus dose, then go to an IV," he notes. "You could potentially start it as bolus dose in the field to get them started, then bring them in, although I haven't actually had anyone try it yet."

Cyclooxygenase (COX) inhibitors "We're looking at inflammatory gene expression, especially those that regulate prostaglandin production via cyclooxygenases COX-1 and COX-2," says Jones. While some prostaglandin is good for healing the gut, certain kinds of prostaglandin contribute to inflammation, too much of which can hamper healing.

"There's a big push for these COX-2 selective inhibitors, because COX-2 is the enzyme that increases during inflammation," Jones notes. But COX-2 isn't all bad--he says it's critical for cardiovascular health because it limits blood clotting (hence the Vioxx controversy). Horses might not have the same cardiovascular side effects with COX-2 inhibitors as humans; equine researchers don't know yet.

"The main reason anti-inflammatory drugs are effective is because they inhibit COX function in some way," explains Jones. "The ones we use routinely in horses--Bute, Banamine, steroids--in some way target the prostaglandin pathways. Blocking prostaglandin is important for treating inflammation and reducing pain; the problem is that prostaglandins (managed by both COX-1 and COX-2) are important for so many things.

"If we can target specific pathways and/or specific cells, we can get better anti-inflammatory drugs that are safer, rather than inhibiting every COX enzyme in the body, which is currently what we do with Bute and Banamine," he says. "What we'd like to do is find a COX-2 inhibitor that's even more selective, affecting a particular cell type rather than body-wide, or under a particular circumstance. We'd maintain those COX-2 functions that are essential and inhibit the ones that are involved in inflammation."

P38 pathway "We've also targeted one very specific pathway regulated by a molecule called P38," Jones says. "P38 is a family of molecules, so there are a bunch of family members in cells that we think we can target more specifically. Plus there are drugs in the pipeline for human medicine that target these molecules. If we can get this proof of principle (show in the lab that these drugs should interrupt specific inflammatory pathways in the horse), these drugs might become available for horses."

Management Studies

"We don't use the hospital population for research, but we do capture data from those horses and do retrospective studies just looking at medical records," says Blikslager. "For example, there's ileal impaction (impaction at the end of the small intestine), which is very big in the Southeast. They tend to get this when fed coastal bermudagrass hay, and we have been able to prove that with these records. Tapeworms contribute to the same problem.

"We'd like to be able to say, 'If you're going to buy coastal bermuda, get it tested first, and if fiber is above a certain level, then your horse is at risk,' " he notes. "That will be the next part of the study."

Preventing and Treating Colic Today

"If you follow these guidelines, you can cut down on colic, and spend less money on grain," Blikslager states. "Plus colic surgery's pretty pricy."

  • Maximize forage intake.
  • Maximize turnout time.

"Picture what horses are designed to do (move around and graze continuously), and simulate that environment," he suggests. "Turn horses out at least 12-18 hours per day, and build a ration from all the hay and grass they can eat, then make up the remainder with grain only if needed. Most breeds honestly could live on a forage-only diet."

If your horse does colic, Blikslager gives the following advice about medications: "Drugs like Bute and Banamine are not all bad, but they should be given by the veterinarian or after consultation with the veterinarian," he says, so the veterinarian can assess the case and determine if further treatment is needed.

"Also, they are one-time drugs; don't just keep giving them to a horse in the same way that you shouldn't keep taking Tylenol or ibuprofen for a severe headache or fever without seeing the doctor," he cautions.

Why They Research Colic

"About 90+% of colics are going to resolve by themselves or with simple medical treatment," says Blikslager. "So we're only dealing with about 10%. And out of those, about 75% leave the hospital, then you lose another 10-15% or so to followup. Really it's a small population of horses (that die from colic), but colic is the leading cause of death.

"So maybe in the end we put a 1-3% dent in that mortality rate, but when you consider that for 9.4 million horses in the country, that's a lot of horses we could save," he states.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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