When it comes to caring for horses with osteoarthritis (OA), management strategies focus on reducing pain, improving joint function, and minimizing deterioration of joint tissues. A variety of therapies exist, including intra-articular (IA, in the joint) medications such as corticosteroids, hyaluronans, and pentosan polysulfates, along with biological agents—stems cells and platelet-rich plasma, for instance.
The most common first line of defense against OA, however, is IA corticosteroids, said Niklas Drumm, DrMedVet, Dipl. ACVS-LA, ECVS, a shareholder and practitioner at Tierklinik Lusche, in Germany. But two relatively new therapies—polyacrylamide hydrogel (PAAG) and stanolozol—might offer alternatives for managing osteoarthritis in horses. He described these during the 2018 British Equine Veterinary Association Congress, held Sept. 12-15, in Birmingham, U.K.
Polyacrylamide hydrogel is a nondegradable synthetic watery gel that integrates safely with soft tissues, said Drumm. It’s been used in human medicine for more than 15 years; doctors primarily use it to treat stress incontinence in women and to reinforce facial tissues.
In horses, veterinarians inject PAAG directly into affected joints. “Two of the proposed modes of action for PAAG are to decrease joint capsule stiffness and viscosupplementation (injecting lubricating fluid into the joint),” Drumm explained.
Studies done on goats as well as horses show that a layer of PAAG persisted in joints for up to two years after injection. In a 2015 study of 43 horses with OA that received IA PAAG, 82.5% were sound 24 months post-treatment, with increasingly more horses becoming sound over time. In another study of 54 racehorses with OA, 83.3% experienced improved soundness.
In a recent study at Drumm’s hospital, he and colleagues evaluated 12 horses with coffin joint OA that received IA PAAG after not responding to previous treatment. He said eight returned to soundness, two improved, and two remained unchanged. He concluded that PAAG is a safe and promising new therapy that has up to 70% success rate return to soundness in refractory (stubborn, unmanageable) OA cases.
This synthetic anabolic steroid has fallen into disfavor and been labeled a banned substance due to its abuse as a performance-enhancing drug in both human and equine athletes, said Drumm. However, it’s been shown to have chondroprotective (joint-protecting) effects.
In a 2015 study of 24 horses with acute or chronic fetlock OA, stanolozol improved lameness in 83.3% of horses administered multiple IA doses of the drug. At 60 days post-treatment, 71.4% of acutely arthritic horses were sound, 95.7% of chronically arthritic horses had improved, and 57.9% of chronic cases were sound.
Drumm said stanolozol is another safe and promising OA therapy, cautioning that “the fact that intra-articular stanolozol for the treatment of joint disease cannot be securely differentiated from the intramuscular application as a performance-enhancing drug remains an issue.”
“While IA corticosteroids are still the first line of defense, (PAAG and stanolozol) can be used as alternatives or additives,” he said.