Excerpt from The Chronicle of the Horse, by Molly Sorge
Parenteral Medications: Tried And True
The two most popular parenteral medications, those given via intravenous or intramuscular injection, are Adequan and Legend. Adequan is the only FDA-approved product of injectible polysulfated glycosaminoglycan and is administered via intramuscular injection. Legend is the only FDA-approved product of injectible hyaluronate sodium administered via intravenous injection. Both products can also be used in intra-articular injections as well.
“The companies that created Legend and Adequan are great companies that really did the research and development,” Richard Markell, DVM, of Ranch and Coast Equine Practice in Encinitas, Calif.
“Adequan incorporates itself into the cartilage and tries to normalize the flexibility and the composition of the cartilage itself. They’ve tested it, so they know it gets to the joint. They put a radioactive dye on it and then injected it into the horse, and then they look at the joint and it lights up in the cartilage,” Markell continued.
Legend works a bit differently; it’s hyaluronic acid. It’s a mechanical lubricant and an anti-inflammatory when it’s put into a joint. There are lots of different brands of hyaluronic acid that people put into joints (Hyvisc, Hylartin V two other examples), and Legend is one of them.
“When it’s injected intravenously, it’s an anti-inflammatory, and it also finds its way to joints and acts as a lubricant,” said Markell.
Using parenteral medications like Adequan and Legend allows the horse’s body to direct the medication where it’s needed. “The body is awesome; it just figures it out,” Markell said. “And rarely do you have just one joint that’s inflamed. Your whole horse is basically in the process of falling apart, and you’ll have inflammation in lots of joints. That’s the cool thing about treating something systemically; it can go to multiple places, and the value of that drug is you get a lot more bang for the buck.”
The catch is that Adequan and Legend are approved as treatments but not as prevention. “We completed a survey of the [American Association of Equine Practitioners] membership, 70 to 80 percent of the vets who responded to the survey were using them in a prophylatic way,” said David Frisbie, DVM and Ph.D. of Colorado State University’s Equine Orthopaedic Research Center. “They’re not getting used for what they’re actually approved for. I’m not suggesting that’s a bad thing, just that they weren’t ever tested in that manner.
“We do believe that parenteral medications do prolong the time period before normal wear and tear catches up to you,” he added. “It’s like saying ‘Can I get more tread life out of my tires if I drive this way?’ ‘If I give my horse Legend, can I go longer before I have to inject a joint?’ There’s some evidence that suggests that that is true, but that’s not been proven definitively.”
If Markell had a client with a limited budget and a horse showing subtle signs of degenerative joint disease, but without lameness, he would recommend a parenteral medication such as Adequan or Legend.
“If I could only pick one, I’d pick injectibles, because there’s been more solid research on them,” he said.
Talk to your vet today about switching from hard-to-get Adequan to Legend.