PSGAG (Adequan®)

BambiandMeghan

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Adequan® is a brand of a substance called polysulfated glycosaminoglycan (this is one of those chemical names that is used to help justify the expense of veterinary school tuition), or PSGAG, for short.  It’s gained popularity as a joint protector, that is, as drug that supposedly protects cartilage, and treats joint inflammation.

PSGAG was first promoted for cases where cartilage damage was thought to be present, with the goal of preventing, slowing, or perhaps even reversing cartilage damage.  However, it wasn’t too long before it was almost routinely given to normal horses, under the rationale that it may help keep normal horses from doing damage to their joints when they are competing.  Like Legend®, or rhinoceros repellant, whether it can actually do all of that is another question.

ASIDE:  I mean, really, how are you supposed to know if your horse is going to develop osteoarthritis anyway?

PSGAG is made up mostly of chondroitin sulfate (CS), which is sometimes fed orally to horses (in any number of oral supplements), and like CS, the product is made, and then modified, from the lung and tracheal tissue of cows.  There are two forms of Adequan®: one is for injection into the joint, and the other is for injection into the muscle.  Even though the product has been approved by the US Food and Drug Administration, it’s not at all clear how well – or even whether – the products are effective, especially when injected into the muscle (the most common route of administration).

madscientistIt’s not like people haven’t studied the stuff.  Early test tube studies on the effects of PSGAG were somewhat contradictory.  Some studies conducted in test tubes on cartilage cells showed positive effects on cartilage, while others showed no effects; some even showed effects that could be construed as harmful. The thing about test tube studies is that the results can’t necessarily be carried over to a living animal – putting drugs into test tubes is a lot different than putting drugs into a horse, mostly because the horse’s body does things to the drug that don’t occur in the test tube (it’s called metabolism).  Horses don’t live in glass houses – or glass vials, either.

Results from studies on living horses don’t provide much in the way of support, either.  So, for example, even though one study conducted in a surgical model of osteoarthritis concluded that Adequan®, given in the joint, reduced joint inflammation and subsequent damage to cartilage caused by chemical injury, the substance absolutely did not help heal damage caused by the surgical procedure.  A more recent study, in 2011, conducted at Colorado State University, found that Adequan® had no measurable effects on any of the measures used in an experimental arthritis model. Under any circumstances, there’s no study that has shown that PSGAG helps heal cartilage damage that is already present.  That means that if your horse has an arthritic joint, you shouldn’t expect that by giving it Adequan® you are going to reverse any of the damage.

dunceAdequan® given in the muscle seems to be a very popular treatment among horse owners.  It’s pretty easy to understand why – people have the idea that it helps prevent joint problems; owners and trainers don’t want their horses to have joint problems.  It has two other things going for it, that, I think, help explain its popularity:

1.  It’s easy to give (just a shot in the muscle)

2.  It’s a lot cheaper than Legend®.

Even so, there is some expense associated with PSGAG, which has led to the curious dosing regimen whereby people give their horses Adequan® once a month.  To me, this makes very little sense.  The label says that you’re supposed to give the injection every four days – I’m not sure how giving it every once in a while is supposed to help anything.  It is cheaper, of course, to give it monthly, instead of all the darn time, but under that rationale, and given the relative lack of supporting evidence, if saving money were the real issue, I’d suggest that you not use it at all!

PSGAG does appear to be very safe.  Then again, a saline injection would be safe, too (although pointless).

Adequan® can be injected directly into the joint; you’re not going to do this, of course, but the product is out there.  Given in the joint, it seems to have a more reliable anti-inflammatory effect, but not obviously anything else.  When it first came out, the company recommended giving weekly injections for five weeks, but, unfortunately, many horse joints weren’t happy with that recommendation, and problems with acute inflammation occurred (joint “flare”) sort of doused people’s enthusiasm for that route of administration. In addition, when compared to other things that get injected into horse joints, such as corticosteroids and hyaluronan, there’s a slightly greater risk of infection with PSGAG; understandably, people might not be inclined to use a product if there’s a significant risk of harm.

The risk of problems from injections of PSGAG into the joint can be greatly reduced by combining it with an antibiotic.  Of course, injecting any substance into a joint is something that should be done by your veterinarian.  Still, you kind of have to wonder if it’s worth the fuss, particularly since other substances, such as corticosteroids, are demonstrably as effective, more consistently effective in research studies, and a lot cheaper.

Oh, one other thing.  There’s also some weak support for using PSGAG injections to treat horses that have injured tendons or ligaments.  So, if your horse hurts his tendon, or strains a suspensory ligament, you can always shoot him with some PSGAG.  But, it’s certainly not something that is going to be critical for a full recovery.

What do I think (how did I know you’d ask)?  Well, more than anything else, when it comes to Adequan® I think that you’re probably paying for your own peace of mind, and putting a price on your good intentions, rather than paying for much of a therapeutic effect.  Although PSGAG can be injected into joints with some reasonable expectation of an anti-inflammatory effect (but not much else), giving it in the muscle is probably not something that’s going to do your horse much good.  And it’s certainly not something that’s going to keep your horse from developing arthritis, that is, if he was ever going to get arthritis in the first place.

If you’re concerned about your horse’s joints, there are a few things that you can do.  Keep your horse at a good weight, don’t ride him too hard, and take care of him.  There’s nothing that prevents joint problems that you can buy in a bottle, can, or plastic tub.

 

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