Study to Examine Combined Use of Lasix, Bisphosphonates

Researchers at the University of Pennsylvania's School of Veterinary Medicine's New Bolton Center have planned a multidisciplinary study to explore the effects of the combined use of Lasix and bisphosphonates in racehorses.

Led by Dr. Mary Robinson, assistant professor of veterinary pharmacology and director of the Equine Pharmacology Laboratory at Penn Vet's New Bolton Center, this landmark study is poised to be the first comprehensive analysis of the two drugs that, when used concurrently could be capable of diminishing bone integrity and compromising cardiac function in racehorses. These effects have the potential to contribute to catastrophic injuries on the racetrack.

"The beauty of this study is that it will use a multi-disciplinary approach to assess the interaction between these two drugs that we know are administered to racehorses," said Robinson. "By coupling our state-of-the art imaging technologies with the scope of expertise among the other investigators on this project, we will be able to produce solid, unbiased data that will address some of the unknowns surrounding the use of these medications."

Nearly 85% of racehorses in the United States receive furosemide, commonly referred to as Lasix, to prevent or reduce the severity of exercise-induced pulmonary hemorrhage. Also used in human medicine to treat heart conditions, the drug is known to cause a short-term loss of calcium and increase the risk of fractures in human patients. But because horses can quickly recover from a calcium deficit, the researchers speculate that Lasix alone is unlikely to be the root cause for catastrophic, racing-related breakdowns which, according to The Jockey Club Equine Injury Database, occur at a rate of approximately 1.6 in 1,000 starts. 

"As racehorse owners and enthusiasts, we have a deep love for the sport and for our horses. There are so many theories about injuries—it's a constant concern—and there's so much to learn, but yet very little has been done in this area in order to so," said Gretchen Jackson. 

She and her husband, Roy Jackson—who owned the ill-fated Barbaro under their Lael Stables—share a passion for improving the welfare of racehorses that lies at the nexus of this study, which is being funded by the Jacksons, George and Julia Strawbridge, and the Pennsylvania State Horse Racing Commission.

"Ultimately, we hope this research will empower us, as an industry, to make more informed decisions or exercise a greater degree of confidence in how we care for these animals that mean so much to us," Gretchen Jackson said.

A team of 13 Penn Vet researchers will explore the largely unknown effects of a class of drugs called bisphosphonates, particularly when being used concurrently with Lasix.

Intended to preserve the integrity of bone in humans, bisphosphonates are commonly used in elderly patients to treat osteoporosis. When administered to young, growing animals, however, the drug may have adverse effects by preventing bone from properly adapting to the forces applied during training—such as those experienced when a horse is at a gallop. 

Because bisphosphonates can linger in the bone for at least one year after the administration of a single dose, there is a heightened chance for interaction with Lasix for horses in training. Bisphosphonates have also been associated with increased risks of heart conditions in humans, including atrial fibrillation, ventricular arrhythmias, and alterations in heart rate variability. 

A collaborative study at its core, the Penn Vet team will cross-examine other facets related to the use of these substances in racehorses, including pioneering new understanding of advanced imaging systems such as New Bolton Center's standing robotic computed tomography and, in collaboration with UC Davis's Dr. Mathieu Spriet, a new standing positron emission tomography system. 

The system, which is identical to the one already in place at Santa Anita Park, will make Penn Vet's New Bolton Center the second veterinary hospital in the world to implement the use of an equine PET scanner.

"This amazing imaging technology is going to be really instrumental in helping us assess the effects—or lack thereof these drugs have on the bone," said Robinson. "It is the most sensitive technique that we have, from an imaging perspective, to look in detail at a horse's legs and see what's going on metabolically." 

"The (PET scan) modality is going to be impactful on a measurable, molecular level. There's no superimposition—or interference—of the structures we are imaging, so we can definitively note any changes in bone turnover in areas as precise as two square millimeters," added Dr. Kate Wulster, assistant professor of clinical large animal diagnostic imaging at Penn Vet. "But the real beauty of using both the PET scan and our robotic CT system in tandem is that we can confidently identify any present morphologic or shape abnormalities within the bone that we know could predispose a horse to fracture. Together, they're going to give us a remarkable amount of information about what is or isn't going on in these horses." 

The research team will be accumulating findings into an innovative, data-driven platform that will be invaluable to objectively assessing national trends in racing-related injuries.

Partnering with Penn Vet's Extracellular Vesicle Core, the first of its kind in the United States, the research team will explore the promising frontier of using EVs in blood or other samples to detect illicit use of bisphosphonates, which are presently undetectable in the blood of a horse after 30 days. 

EVs are membrane-enclosed nanoparticles released from all cell types and play an integral role in intercellular communication. Because they possess tissue-specific characteristics representative of the cells in which they came from, they hold the potential to provide non-invasive, rapid diagnostic solutions to test for the presence of illegitimate drug use. 

"The field of EV research is a vastly promising and explosive area of study. By harnessing the unique communicative power of EVs, we hope to redefine how we can utilize blood samples in order to proactively safeguard the health and well-being of these tremendous athletes," said Dr. Andrew Hoffman, the Gilbert S. Kahn Dean of Veterinary Medicine and principal investigator of the EV Core Facility.

"Beyond detecting illegitimate substance use, these biomarkers also offer the means of identifying otherwise indiscernible, but significant, changes in the horse's biological health that could serve as warning signs of an increased risk for catastrophic injury," said Hoffman.

"Our hope is to eventually harness the information carried in these vesicles to develop a hand-held, stall-side diagnostic tool that could be used on race day to make sure horses are healthy enough to compete safely, as well as by trainers in the field to continuously evaluate any changes in their horse's well-being, and when additional veterinary care may be needed," elaborated Robinson.

While efforts for this research project are underway, the study is estimated to take two years to complete. 

"This multidisciplinary, prospective approach will provide us with the most comprehensive data available to assess if the use of these substances may or may not be contributing to catastrophic injuries on the track," said Robinson. "At the end of the day, we're dedicated to ensuring that we are doing everything in our power to provide owners, breeders, and trainers with sound, unbiased insights to keep their horses safe."

 Dr. Mary Robinson is an assistant professor of veterinary pharmacology and director of the Equine Pharmacology Laboratory at the University of Pennsylvania School of Veterinary Medicine. Dr. Kathryn Wulster is an assistant professor of clinical large animal diagnostic imaging at Penn Vet. Dr. Andrew Hoffman is the Gilbert S. Kahn Dean of Veterinary Medicine and Principal of the EV Core Facility. 

Additional investigators on the study include Penn Vet's Faculty and Staff including Dr. Kyla Ortved, Dr. Cristobal Navas de Solis, Dr. Claire Underwood, Dr. Virginia Reef, Dr. Darko Stefanovski, Dr. Rachel Derita, Dr. Joanne Haughan, Dr. Youwen You, Dr. Jinwen Chen, and Dr. Zibin Jiang.