When nutraceuticals are no longer making a difference in a horse’s joint pain, many veterinarians will suggest, ”You could try Adequan or Legend.” While your veterinarian will decide which is best for your horse, it’s wise for you to understand the difference between these two drugs.
Both Adequan (www.luitpoldanimalhealth.com) and Legend (www.animalhealth.bayerhealthcare.com) have a similar action. They’re believed to inactivate or ”tie up” destructive enzymes in the joint fluid, or slow their release by the synovial membrane, slowing/stopping the destruction of cartilage and hopefully giving it a chance to heal. Both drugs also stop white-cell invasion into the joint, although this may be a secondary effect related to their ability to block inflammation. Both drugs also increase the viscosity of joint fluid.
Adequan (polysulfated glycosaminoglycans or PSGAG) was first approved for injection directly into joints. That drug received approval for the treatment of degenerative or traumatic arthritis of the carpus (knee) and associated lameness. The studies submitted to the FDA in support of intramuscular Adequan first established that drug levels within the carpus were equivalent to those seen when joints were injected and also demonstrated therapeutic levels in the hock. This was found for both normal horses and horses that had a defect created surgically in the cartilage of one carpus.
Legend (injectable hyaluronate-sodium injectable solution) is specifically approved for treatment of joint dysfunction of the carpus or fetlock due to noninfectious synovitis associated with osteoarthritis.
Neither of these drugs is FDA-approved as a preventative, and the documented effects of both drugs applies only when they are used at the dosages and dosing intervals specified on the label.
Adequan is labeled to be injected at four-day intervals for a total of 28 days, while Legend should be given weekly for up to three consecutive weekly treatments. It’s important to understand that these dosing intervals are based on studies that monitor both the clinical effectiveness and the levels of the drug in the joint.
If your horse has no symptoms of arthritis, there’s really nothing about the way these drugs work that would make either one a logical choice to prevent arthritis.
A case could be made for treating early joint problems before they become a major problem, but a single injection of either drug is not going to have effects that last a month. There’s just not enough information available to know if using either drug this way can really help prevent joint problems.
The cost for each is close. Adequan will cost about $300 for a 28-day series, while Legend will run $250 or so for 21 days. As for which drug is better, if you’re talking about treatment, Legend is typically recommended if the problem is synovitis (inflammation of the synovial membrane of the joint) or Adequan if there are known to be cartilage lesions. However, in real life you rarely know with certainty what’s actually going on inside the joint and the two drugs do work similarly. The choice between the two has to be made on how the horse responds.