Researchers eye clopidogrel uses, efficacy for veterinary patients

Athens, Ga. — Veterinary researchers at the University of Georgia (UGA) say that clopidogrel is showing promise as a veterinary therapy.

According to Benjamin M. Brainard, VMD, assistant professor of critical care at UGA's College of Veterinary Medicine, a key finding from a study he led is that clopidogrel may offer a safe alternative to NSAIDs for treating dogs at risk of thromboembolism because of the concurrent therapeutic use of corticosteroids such as prednisone or dexamethasone. Clopidogrel is approved for use in people under the trade name Plavix.

Other than aspirin, there are no approved anti-platelet drug therapies available to prophylactically treat companion animals with known or suspected hypercoagulability, Brainard explains. While clopidogrel is currently more expensive than aspirin, he says it seems to demonstrate better anti-platelet effects, which may make it a more effective drug for platelet aggregation or activation.

"The combination of aspirin and corticosteroids is a potentially deadly combination, as it can result in severe gastrointestinal damage, including ulceration and even perforation," Brainard explains. "The ability to have an alternate drug to decrease platelet activity that does not have potential interactions (with corticosterioids) is a huge benefit."

The study of nine healthy, mixed-breed dogs found that most had a significant inhibition of platelet function within three hours of receiving clopidogrel. All of the dogs tolerated the drug well and showed no adverse effects. Platelet activity returned to normal levels within approximately one week after the drug was discontinued, which is similar to the response found in humans.

Clopidogrel, which is only available as an oral therapy, has been safely administered to cats, rabbits and calves; and the UGA laboratory recently finished a similar study evaluating its use in horses, with similar results as those found in the dog study.

The next step, Brainard says, is to take the results and techniques of this study and apply them to dogs with critical illnesses that may be at risk for thromboembolic disease.

"While we established that this drug works at a certain dose in healthy dogs, the application in sick animals may show different drug activity or distribution," he explains. "We suspect that platelets in dogs with immune-mediated hemolytic anemia, for example, are hyper-reactive, making them prone to pulmonary thromboembolism. Our institution and others are investigating the use of clopidogrel in these patients to see if we can decrease the morbidity and mortality of this disease."

Brainard adds the UGA lab is interested in examining other anti-platelet and anti-coagulant drugs labeled for human use to search for potential applications for veterinary medicine.

The research team also included Stephanie A. Kleine, DVM, at Georgia Veterinary Specialists; Mark G. Papich, DVM, MS, professor of clinical pharmacology at North Carolina State University and Steven C. Budsberg, DVM, MS, professor of orthopedic surgery in the UGA veterinary college.