Why is There No Adequan® or Legend® for People?


Do you ever wonder why there is no Adequan® or Legend® for people?  I mean, these are approved medications for horses – they’re sold by the gallon to help prevent and/or treat osteoarthritis in horses.  They sound just fantastic = look at what they say (from their websites).

Adequan®: “DIMINISH the destructive processes of degenerative joint disease.  REVERSE the processes which result in the loss of cartilage components. IMPROVE overall joint function and associated lameness.”

Legend®: “By decreasing the production and release of inflammatory mediators, LEGEND helps reduce joint inflammation and the resulting pain and lameness. The interleukin-1-driven production and release of prostaglandin and also the protein count in synovial fluid is decreased for 45 days following I.V. injection, indicating a beneficial effect long after I.V. administration.”

NOTE:  In this article, I am talking about the intravenous use of hyaluronan (Legend®).  Similar products are certainly injected into joints, although there is a lot of discussion in the human medical literature about how useful they really are.

Both products are approved by the United States Food and Drug Administration.  However, both products are only sold to horse owners (well, there is an Adequan® product for dogs).  If you go just based on what the companies say that these products do, assuming that someone could afford them, you’d have to wonder why everyone wouldn’t use the products for their horse(s).

Osteoarthritis is a crippling bone and joint disease in horses.  Of course, but it’s a crippling bone and joint disease in humans, too.  There are a lot of similarities between the two species; joints have much more in common they have differences across species.  In fact, horses are even used as a model in which to study the disease in humans.  Since that’s the case, though, it does make one wonder, “If the products are so great in horses and osteoarthritis is pretty much the same disease in all species, how come the drugs aren’t used in people?”  As great as the market for the products apparently is in horses, you’d think that the market in human medicine would be exponentially higher (that is, there would be a LOT more money in it).  So – and to answer a question posed to me – why isn’t it sold for use in people?

Honestly, the answer is pretty simple.  I’m almost positive that they don’t market these drugs to people because it can’t be shown that the products work in people.  “But,” you say (because you’re like that), “how is it they can be shown to “work” in horses but not in people?”

Which is a reasonable question.

Again, the answer is surprisingly simple.  You see, the process for approval of new drugs for animals is quite different than that for the approval of new drugs for people.  The process is quite a bit easier and quite a bit less expensive when it comes to approving drugs for animals, when compared the process for people.  It’s just a fact that products intended for use in animals get through the approval process with a different level of scrutiny than that which is directed towards products intended for use in humans.  Let’s take a look.


To get the process started, the sponsor does the initial work.  The sponsor is the company trying to get the drug approved.

For Animals – The drug sponsor collects information about the safety and effectiveness of a new animal drug.  The sponsor may need to conduct studies to get this information.  For any studies that are performed, the sponsor analyzes the results.

For People, you’ve got –

  • Preclinical (animal) testing.
  • An investigational new drug application (IND) outlines what the sponsor of a new drug proposes for human testing in clinical trials.
  • Phase 1 studies (typically involve 20 to 80 people).
  • Phase 2 studies (typically involve a few dozen to about 300 people).
  • Phase 3 studies (typically involve several hundred to about 3,000 people).

So, for starters, drugs for humans are tested a whole lot more stringently than are drugs for animals. Plus, the testing is done on a many more individuals.  Interestingly, for animals, all of the initial testing and analysis is done by the sponsor on the sponsor’s own terms (sort of a fox guarding the hen house thing, actually).


  • For Animals – Based on the collected information, including any study results, the sponsor decides if there is enough proof that the drug is safe and effective to meet the requirements for approval. The sponsor submits a New Animal Drug Application (NADA) to CVM.  The NADA includes all the information about the drug and the proposed label.
  • For humans –  
  • There’s a pre-NDA period, just before a new drug application (NDA) is submitted. This is a common time for the FDA and drug sponsors to meet.
  • Next is a submission of Submission of an NDA. This is the formal step asking the FDA to consider a drug for marketing approval.
  • After an NDA is received, the FDA has 60 days to decide whether to file it so it can be reviewed.

For animals, the sponsor gets to decide pretty much everything prior to making any submission.  That’s not how things work when it comes to human drugs.  There’s a higher level of scrutiny for human drugs.


  • For Animals – A team of Center for Veterinary Medicine (CVM) personnel, including veterinarians, animal scientists, biostatisticians, chemists, microbiologists, pharmacologists, and toxicologists, reviews the NADA.  If the center’s team agrees with the sponsor’s conclusion that the drug is safe and effective if it is used according to the proposed label, CVM approves the NADA and the drug sponsor can legally sell the drug.

This all sounds very collegial, doesn’t it?  But don’t just take my word for it.  You can learn more about the process for approving animal drugs IF YOU CLICK HERE.

  • For Humans –
  • If the FDA files the NDA, an FDA review team is assigned to evaluate the sponsor’s research on the drug’s safety and effectiveness.
  • The FDA reviews information that goes on a drug’s professional labeling, which providers information on how the drugs should be used.
  • The FDA inspects the facilities where the drug will be manufactured as part of the approval process.
  • FDA reviewers will approve the application or issue a complete response letter.

You can learn more about the process for human drugs IF YOU CLICK HERE.

Given that Adequan® was approved in the mid-1980’s and that Legend® was approved not too long thereafter, there’s certainly been plenty of time to get the products approved for use in human medicine.  But they’re not.  For my way of thinking, there are only a few options.

  1. The products can’t be shown to work in humans.
  2. The manufacturers have other things to do besides rake in the buckets of money that would come to them should such products actually work. Maybe, rather than spending the necessary time indoors doing laboratory and statistical analysis, they’d rather be at the beach, wine tasting, or hiking on a sun-washed trail.
  3. There’s conspiracy being directed by the Deep Arthritis State (DAS) to prevent these drugs from ever coming to market so that the DAS can continue to not really help people with arthritis and make lots more money… wait, they’d be able to sell the drugs to people, too… maybe this isn’t such a good choice.
  4. The lab folks are lazy. Granted, this would be over 3 decades of lazy, and most lab folks that I’ve met are anything but lazy, but I’ve been known to want to stay on the couch, too.

I suppose I could go on but then the article would get too long.  I could point out, for example, that the latest reference from the Legend® website is from 1997 and that the study in question had a number of measured endpoints where no effect was shown.  I could note that one of the main studies that Adequan® uses to support their product is from 1993 and it’s not published in a journal that is followed by PUBMED, the online site that, “…comprises more than 28 million citations for biomedical literature from MEDLINE, life science journals, and online books.”

The bottom line, however, is that these products got approved for a very different process than the process that is used to approve human drugs.  It’s certainly less stringent.  Whether that’s a good thing or not is debatable, I suppose, but the fact is that they’re not approved for use in people.  And, if you’re wondering whether I think these products really do anything of importance for the horse’s health, well, I haven’t prescribed them in years.

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