Medication | Horse Racing Free Tips

Pros And Cons Of Antibiotic Injections In Equine Joints

Because of the finesse with which equine veterinarians inject medications into joints, the procedure can appear uncomplicated. While injecting joints with antibiotics can help clear infections, the procedure is not without risks. Veterinarians must therefore consider a number of important factors before moving forward with intra-articular antibiotic therapies.

Managing Osteoarthritis

Medicating joints with corticosteroids, polysulfated glycosaminoglycans, or hyaluronic acid is commonplace in equine sports medicine. Intra-articular injection is often used in conjunction with other modalities, including oral joint health supplements. Oral products decrease inflammation and improve mobility, boosting the overall health of joints. Examples of appropriate products include high-quality supplements that contain proprietary combinations of glucosamine hydrochloride, chondroitin sulfate, MSM, and hyaluronic acid.

According to a recent review of intra-articular antibiotic use, 78 percent of veterinarians use intra-articular antibiotics in combination with other medications.^* By adding an antibiotic, often amikacin, to corticosteroid or polysulfated glycosaminoglycan, veterinarians hope to sidestep the development of a septic joint.

Considering the low risk of infection following joint injections, the question then becomes whether or not veterinarians should use prophylactic antibiotics. Moreover, because intra-articular antibiotics are used “off-label,” no researched guidelines for appropriate intra-articular use exist.

Prophylactic intra-articular antibiotic use therefore has two major ramifications:

Veterinarians may administer an excessively high dose. “According to some evidence, antibiotics like amikacin have toxic effects on cartilage cells and other joint tissues,” said Peter Huntington, B.V.Sc., M.A.C.V.Sc., director of nutrition at Kentucky Equine Research.
Unnecessary use of antibiotics contributes to antibiotic resistance. “With few new antibiotics in development and growing multidrug resistance to currently available medication, revisiting the practice of prophylactic antibiotic use in horses may be warranted,” Huntington added.

These concerns associated with intra-articular antibiotic administration supports alternative strategies for maintaining joint health.

Managing Septic Joints

Intra-articular antibiotics are indispensable in the face of a septic joint because direct administration into the joint can achieve high local drug concentrations. If, on the other hand, antibiotics are offered orally, high dosages would be needed for longer durations to achieve the same result as an intra-articular injection.

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“Systemic antibiotics, however, may be associated with important and potentially life-threatening side effects such as gastrointestinal disturbances that disrupt the microbiome. In the face of microbiome disarray, pathogenic bacteria may proliferate, altering immunity and increasing the risk of diarrhea or laminitis,” Huntington explained. When systemic antibiotics must be administered, gastrointestinal support in the form of research-proven supplements should be considered.

Local antibiotic delivery directly into a joint may also:

Improve owner compliance as injections do not rely on the owner administering the entire course of oral antibiotics;
Make treatment more affordable, as a systemic antibiotic maybe be cost prohibitive for an owner;
Shorten the course of treatment and improve outcomes; and
Result in high concentrations at the site of infection that may be particularly useful for fighting “floating biofilm,” which is an accumulation of microbes embedded within a self-produced extracellular matrix that helps protect the bacteria from antibiotics.

^*Pezzanite, L.M., D.A. Hendrickson, S. Dow, L. Chow, D. Krause, and L. Goodrich. 2021. Intra-articular administration of antibiotics in horses: Justifications, risks, reconsideration of use and outcomes. Equine Veterinary Journal:13502.

Doug O’Neill Fined $5,000 In Settlement Agreement With CHRB

Trainer Doug O'Neill has been issued a $5,000 fine by the California Horse Racing Board pursuant to a settlement agreement, according to a stewards' ruling dated Dec. 31, 2021. The fine was issued for failing to post five “detention stall signs” at Los Alamitos on July 5, 2021, and is listed is a violation of CHRB Rule #1845 (c)(2)(A) (Authorized Bleeder Medication).

The original complaint was filed on Oct. 22, stating that investigators received a tip that a horse from O'Neill's barn that had already been entered in a race may have received illegal medication. Investigators at Los Alamitos inspected the barn on July 5 and discovered the unidentified horse did not have a sign on its stall door indicating it was running within the next 24 hours.

Assistant trainer Sabas Rivera told investigators he had treated the horse the previous day with oral pastes called Bleeder Shield and Un-Lock, which meant they had been treated within 24 hours of race time.

Un-Lock is marketed as a supplement containing amino acids and electrolytes to reduce muscle fatigue and prevent tying up. Bleeder Shield purports to contain the Chinese herb Yunnan Baiyao to prevent exercise-induced pulmonary hemorrhage. Neither product is approved by the Food and Drug Administration because the FDA does not inspect or approve dietary supplements for horses or humans. California rules do allow the administration of oral pastes like these, but not within 24 hours of a race.

In 2013, O'Neill appeared before California stewards after a barn foreman administered an amino acid paste to runner Cinco de Mario, who was entered to run within 24 hours. Cinco de Mario was subsequently scratched from the race. At the time, O'Neill said the foreman made a mistake and was meant to give the paste to a horse in the next stall who was more than 24 hours out from a race. At the time, the trainer also said he would time the administration of oral supplements like that one 25 to 30 hours out from a horse's race, because he believed they could still be effective in that window without violating the rules. He received a $1,500 fine in that case.

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Heaves And Heart Failure: Is There A Connection?

A new study out of Canada shows that uncontrolled respiratory disease in horses may put them at risk for pulmonary artery changes that lead to heart failure.

People with severe asthma can have thickening of the pulmonary arteries, which leads to pulmonary hypertension. Severe equine asthma, like asthma in humans, presents as airway inflammation, coughing and labored breathing; therefore it's feasible that equine asthma can also lead to pulmonary artery thickening, reports EQUUS magazine.

Often called “heaves,” this condition is triggered by mold or dust in hay or the environment. The affected horse must be managed so exposure to these environmental triggers is minimized. Best management practices for horses with heaves include as much turnout as possible, removing horses from stalls when they are cleaned and rebedded, and soaking hay.

Dr. Serena Ceriotti and other researchers at the University of Montreal looked at multiple post-mortem lung samples from 18 horses — six that were in heaves episodes when they died; six with heaves that was in remission because of management practices; and six with no history of heaves.

The scientists measured arterial thickness and found that the horses experiencing active heaves episodes had thicker arteries than the other horses.

Though it's unclear why the arteries thicken, experiments in rodents suggest the low oxygen content and inflammation may increase smooth muscle in the arterial wall. This increase in the muscle decreases the area for blood to flow and may increase muscle contractions, which leads to pulmonary hypertension, minimizing blood flow and limiting cardiac function. This condition can eventually lead to the enlargement and failure of the right ventricle of the heart.

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A second portion of the study tested two potential pulmonary hypertension treatments on live horses. One involved reducing the horse's exposure to dust for an entire year and on using hay alternatives. The second used the medication fluticasone for six months then added in dust-control strategies for an additional six months.

The researchers found that both treatments lead to a reversal in artery wall thickness, but this could only be seen once the dust control measurements were enacted. The team notes that hay is the main trigger for heaves; often just changing the horse's diet to include a forage alternative is enough to control the disease.

They conclude that arterial wall remodeling is reversible, but only with strict dust control measures. Inhaled corticosteroids can rapidly improve a horse in experiencing a heaves flareup, but an improved environment is the only way to manage the condition long term.

Ins And Outs Of Transdermal NSAID In Horses

If you're fighting tooth and nail to administer oral medications, the introduction of a transdermal option often pleases horses and handlers alike. Transdermal medications are applied to the surface of the skin, typically in the form of an ointment or gel, so as to allow gradual absorption into the body. Are you considering transdermal medications, especially anti-inflammatories? If so, it's important to understand how these drugs are absorbed and eliminated, particularly if your horse is involved in competition and subject to stringent drug withdrawal times.

In the U.S., a transdermal formulation of the nonsteroidal anti-inflammatory (NSAID) diclofenac sodium, sold under the brand name Surpass, is approved for use in horses. Recently, a transdermal product containing flunixin meglumine was approved in cattle and is therefore available for off-label use in horses. Flunixin meglumine is often called by the common brand name Banamine.

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To assess how transdermal delivery of flunixin meglumine behaves in the body compared to other routes of administration (e.g., oral, intravenous, intramuscular), researchers applied a 10-mL dose of transdermal flunixin meglumine along the midline of the horse's back, from the withers to the tailhead. This was equivalent to a standard 500-mg dose of flunixin meglumine per horse. *

Blood and urine samples were intermittently collected for up to 96 hours after administration to measure the intricacies of how the medication is absorbed and cleared, a science known as pharmacokinetics.

“Transdermal application was well tolerated in all six study horses, with no horse showing any negative dermal effects,” said Peter Huntington, B.V.Sc., M.A.C.V.Sc., director of nutrition at Kentucky Equine Research.

In terms of the drug's behavior, here's what the research team found:

The maximum concentration of flunixin meglumine in blood was only an average of 515 ng/mL, which is much lower than oral and intramuscular concentrations. Oral administration of a comparable dose of flunixin meglumine results in average concentrations ranging from 3,340 to 7,200 ng/mL. Intramuscular flunixin meglumine reaches average concentrations of 1,799-3,269 ng/mL.
Transdermal absorption into the horse's bloodstream was slow, an average of 8.76 hours. Oral flunixin meglumine requires less than an hour to be absorbed.
Elimination (clearance) of transdermal flunixin meglumine was also much slower than other routes of administration. It took 22 hours for half of the drug to be eliminated from the bloodstream (called the half-life) when the transdermal formulation was used. In contrast, the intravenous half-life is 3.38-9.68 hours.
The data also showed that transdermal flunixin meglumine has unique pharmacokinetics called “flip-flop kinetics” in which the rate of absorption is actually slower than the rate of elimination.

“Based on this data, it is not surprising that flunixin meglumine and a metabolite were still detectable in urine 96 hours after application. This means that the withdrawal time for transdermal flunixin meglumine would be longer than for any other route of administration,” said Huntington.

He added, “Even though the blood concentrations of flunixin meglumine were lower compared to those achieved by other routes, the slow, variable absorption and 'flip- flop kinetics' indicate the medicine applied transdermally persists in the body longer than if given by other routes of administration. More excretion studies in exercising horses are needed before safe withholding periods before competition can be established.”

Despite the low circulating drug concentrations, transdermal flunixin meglumine still elicited an anti-inflammatory effect for up to 72 hours after application.

In terms of safety, Huntington warned, “Considering that transdermal flunixin meglumine is indeed absorbed systemically, this means that horses are at risk of the common side effects associated with NSAIDs administered by other routes: gastric ulceration, dorsal colitis, and disruption of the intestinal microbiome.”

Horses treated with any type of NSAID by any route of administration, including transdermal, would therefore benefit from a digestive tract supplement containing antacids, stomach-coating agents, and a hindgut buffer.

“These supplements reduce the risk of damage to the gut lining or change in the microbiota resulting from NSAID use,” Huntington advised.

*Knych, H.K., R.M. Arthur, S.R. Gretler, D.S. McKemie, S. Goldin, and P.H. Kass. 2021. Pharmacokinetics of transdermal flunixin meglumine and effects on biomarkers of inflammation in horses. Journal of Veterinary Pharmacology and Therapeutics:12993.

Reprinted courtesy of Kentucky Equine Research. Visit ker.com for the latest in equine nutrition and management, and subscribe to Equinews to receive these articles directly.

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