Adequan vs Polyglycan for Horses: What Is the Difference?

By Dr Duncan Houston

Horse arthritis treatment can get confusing very quickly.

Owners hear about Adequan, Legend, Polyglycan, hyaluronic acid, PSGAG, pentosan, joint injections, “maintenance programs,” “generics,” and off-label products. Then someone at the barn says one product is “basically the same thing but cheaper,” and suddenly a medical decision becomes a group chat with needles.

The most important point is this: Adequan and Polyglycan are not the same product, and Polyglycan is not a generic version of Adequan.

That does not mean every horse needs Adequan. It does not mean Polyglycan is never discussed by veterinarians. It means owners should understand the difference between an FDA-approved arthritis medication and a product marketed for synovial fluid replacement or lavage, especially when joint disease is being treated long term.

Quick Answer

Adequan is an FDA-approved intramuscular polysulfated glycosaminoglycan, or PSGAG, recommended for the treatment of non-infectious degenerative or traumatic joint dysfunction and associated lameness of the carpal and hock joints in horses. Polyglycan is a different product containing hyaluronic acid, chondroitin sulfate, and N-acetyl-D-glucosamine, marketed as a synovial fluid replacement, post-surgical lavage, or viscosupplement, and it should not be described as a generic Adequan. FDA approval matters because an approved animal drug has been reviewed for safety, effectiveness, strength, quality, purity, and truthful labelling when used according to its label. (DailyMed)

What Is Adequan?

Adequan i.m. is the brand name for polysulfated glycosaminoglycan, often shortened to PSGAG.

It is labelled for intramuscular use in horses and is recommended for non-infectious degenerative or traumatic joint dysfunction and associated lameness of the carpal and hock joints. The labelled dose is 500 mg intramuscularly every 4 days for 28 days, for a total of 7 injections. The label also specifically states that it is not for intra-articular use. (DailyMed)

In plain English, Adequan is an injectable prescription medication used by veterinarians as part of managing certain arthritic or degenerative joint problems in horses.

Important Adequan points:

• It is a PSGAG.

• It is given intramuscularly.

• It is not injected directly into the joint.

• It is FDA-approved under NADA #140-901.

• Its labelled equine indication is for carpal and hock joint dysfunction associated with non-infectious degenerative or traumatic joint disease.

• It should be used under veterinary direction.

The clinical mistake is thinking Adequan is just a “joint supplement injection.” It is not. It is a prescription animal drug with a defined label, dose, route, and indication.

What Is Polyglycan?

Polyglycan is a different product.

It contains hyaluronic acid, sodium chondroitin sulfate, and N-acetyl-D-glucosamine. The product’s own website describes it as a patented formulation designed to replace lost or damaged synovial fluid, with equine administration involving instillation into the synovial space. Polyglycan’s product information describes it as a synovial fluid replacement, post-surgical lavage, or viscosupplement. (Polyglycan)

That makes it very different from Adequan.

Adequan is a PSGAG prescription drug labelled for intramuscular use.

Polyglycan is a combination product marketed around synovial fluid replacement or lavage.

Those are not the same thing.

In 2019, the FDA issued a warning letter to Bimeda about Polyglycan, Polyglycan-SA, Polyglycan-HV, and related products, stating that the products were being marketed with claims that made them unapproved new animal drugs and that they were not the subject of an approved new animal drug application, conditional approval, or index listing. (U.S. Food and Drug Administration)

That regulatory history is important because owners may hear Polyglycan discussed as if it is simply a cheaper version of an approved arthritis medication. That is not accurate.

What Is Legend?

Legend is hyaluronate sodium, also called sodium hyaluronate or hyaluronic acid.

It is FDA-approved for the treatment of joint dysfunction of the carpus or fetlock in horses due to non-infectious synovitis associated with equine osteoarthritis. Its label includes both intravenous and intra-articular routes, depending on the situation and veterinary decision-making. (DailyMed)

Legend is often discussed alongside Adequan because both are established injectable joint medications in horses, but they are not the same drug.

A simple way to think about it:

The important owner takeaway is not “one is always better.” It is that these products are not interchangeable.

Is Polyglycan a Generic Adequan?

No.

Polyglycan is not a generic Adequan.

A generic animal drug goes through an FDA Abbreviated New Animal Drug Application, or ANADA, process. The FDA explains that an approved animal drug has gone through the NADA process, and an approved generic animal drug has gone through the ANADA process. Approval means the drug is safe and effective when used according to the label, and that strength, quality, purity, and labelling standards are met. (U.S. Food and Drug Administration)

A true generic has to match an approved reference drug in the way required by regulators. It is not just “similar idea, cheaper bottle.”

For example, NexHA is an FDA-approved hyaluronate sodium product approved under an ANADA and labelled for treating carpus or fetlock joint dysfunction in horses due to non-infectious synovitis associated with osteoarthritis. That is the kind of regulatory pathway owners should think of when they hear the word “generic.” (DailyMed)

Polyglycan does not become generic Adequan just because both are discussed in joint-health conversations.

That is barn pharmacology, and barn pharmacology can get expensive fast.

Why FDA Approval Matters

FDA approval is not just a marketing badge.

For animal drugs, FDA approval means the product has been reviewed for safety and effectiveness when used according to the label. It also means the drug’s strength, quality, purity, and labelling have been reviewed. (U.S. Food and Drug Administration)

That matters because horses are not labelling experiments with legs.

When a veterinarian chooses a joint medication, they are thinking about:

• Diagnosis

• Joint involved

• Severity of lameness

• Route of administration

• Evidence for that product

• Safety profile

• Competition rules

• Drug interactions

• Infection risk

• Owner budget

• Whether the medication is being used according to label

• Whether there is a better approved option

FDA approval does not mean a drug is perfect. It does not mean every horse responds. It does not mean it is the only possible treatment.

But it does mean there is a defined regulatory standard behind the product for its labelled use.

What About the Adequan vs Polyglycan Comparison Study?

There is a commonly referenced veterinary discussion comparing Adequan and Polyglycan in horses with induced joint inflammation. That discussion reported better improvement in lameness and joint swelling in the Adequan group than in the Polyglycan group. (Vin)

That information is worth knowing, but I would be careful about building an entire treatment plan around a single head-to-head summary.

In practice, I care about several things:

• What is the actual diagnosis?

• Which joint is involved?

• Is the problem synovitis, osteoarthritis, soft tissue injury, subchondral bone pain, infection, or something else?

• Is this a systemic medication decision or an intra-articular treatment decision?

• Is the product approved for the intended use?

• What evidence supports that use?

• What is the risk if the product is injected into or around a joint?

• Is the horse competing under medication rules?

• What happens if this treatment does not work?

The bigger point is still clear: Polyglycan should not be presented to owners as “generic Adequan.” It is not.

What About Zycosan and Pentosan?

This is worth mentioning because the equine joint medication landscape has changed.

Zycosan, which contains pentosan polysulfate sodium, was FDA-approved for the control of clinical signs associated with osteoarthritis in horses. The FDA described it as the first injectable pentosan product to receive FDA approval for horses. (U.S. Food and Drug Administration)

So the current discussion is not only Adequan, Legend, and Polyglycan.

There are now additional FDA-approved injectable options for equine osteoarthritis, and your veterinarian may consider them depending on the horse, diagnosis, country, availability, competition rules, and treatment goals.

The practical message is not “use this one product.”

The practical message is: use a diagnosis-based plan with approved products when appropriate, rather than choosing joint treatments based on price, popularity, or barn recommendations.

Which Product Is Best for Horse Arthritis?

There is no single best product for every horse.

Arthritis is not one identical disease in every patient. A 6-year-old jumper with early hock changes, a 19-year-old trail horse with chronic fetlock osteoarthritis, a racehorse with carpal synovitis, and a dressage horse with subtle performance loss may all need different plans.

A good arthritis plan may include:

• Lameness examination

• Flexion tests

• Hoof assessment

• Diagnostic nerve or joint blocks

• Radiographs

• Ultrasound where appropriate

• Joint fluid testing in selected cases

• Corrective farriery

• Weight control

• Exercise modification

• NSAIDs when appropriate

• Intra-articular therapy

• Systemic joint medication

• Rehabilitation

• Competition medication planning

• Monitoring response over time

Joint medication should not be chosen before the problem is properly understood.

The mistake I see most often is owners treating “arthritis” as a single vague label. The more accurate question is: which joint, which tissue, which stage, which pain generator, and what are we trying to improve?

Risk Framework: How Worried Should You Be?

Low Risk

Low risk means your horse has mild stiffness, is still comfortable, has no major lameness, and your vet has already diagnosed a manageable osteoarthritis pattern.

Action: Discuss long-term management, farriery, workload, weight, and whether an approved systemic joint medication such as Adequan, Legend, Zycosan, or another option is appropriate.

Moderate Risk

Moderate concern includes recurrent stiffness, mild to moderate lameness, reduced performance, difficulty warming up, joint filling, or needing repeated anti-inflammatory medication to stay comfortable.

Action: Book a lameness workup. Medication choices should be based on the joint involved and the diagnosis, not just product reputation.

High Risk

High concern includes worsening lameness, marked joint swelling, heat, severe pain after work, poor response to previous treatment, or unclear diagnosis.

Action: Involve your veterinarian before giving another injection or changing products. Imaging, nerve blocks, or joint fluid testing may be needed.

Critical Risk

Critical concern includes severe lameness after a joint injection, a hot swollen joint, fever, depression, non-weight-bearing lameness, sudden severe joint pain, or rapidly worsening swelling.

Action: Treat this as urgent. A septic joint is an emergency. Intra-articular injections require strict aseptic technique because infection inside a joint can be catastrophic. Legend’s label specifically warns that strict aseptic technique is required for intra-articular injection and that precautions are needed to prevent swelling or infection. (DailyMed)

What Else Could Look Like Arthritis?

Not every stiff or lame horse has arthritis.

Important rule-outs include:

• Hoof imbalance

• Long toes and low heels

• Hoof abscess

• Laminitis

• Navicular-region pain

• Tendon or ligament injury

• Suspensory disease

• Back or sacroiliac pain

• Muscle soreness

• Poor saddle fit

• Dental or bit-related resistance

• Neurological disease

• Fracture or stress injury

• Subchondral bone disease

• Joint infection

• Poor conditioning

• Overtraining

• Rider or tack changes

This is why “joint injections” should not be the first answer to every performance issue.

A horse that feels short-striding may need a farrier. A horse that resists collection may have back pain. A horse that warms out of stiffness may have joint disease, but it may also have soft tissue pain or poor conditioning.

Treatment without diagnosis is how owners spend money while the real problem keeps trotting along smugly in the background.

When Is This an Emergency?

Call your veterinarian urgently if your horse has:

• Sudden severe lameness

• Non-weight-bearing lameness

• A hot, swollen joint

• Fever

• Depression or not eating

• Severe pain after a joint injection

• Drainage from an injection site

• Rapidly worsening swelling

• Lameness with a wound near a joint

• Suspected puncture into a joint

• Severe swelling after intra-articular treatment

• Signs that worsen over hours rather than days

A joint infection is not a “wait until Monday” problem. If bacteria enter a joint, cartilage damage can happen quickly and the horse may need urgent veterinary treatment, lavage, antibiotics, and hospital care.

What Should Owners Do Before Choosing a Joint Product?

1. Get a diagnosis first

Do not start with “Which injection should I buy?”

Start with “What is causing the lameness?”

That may require an exam, radiographs, nerve blocks, ultrasound, or referral.

2. Ask what the product is approved for

Useful questions include:

• Is this FDA-approved for horses?

• What is the labelled indication?

• What route is it labelled for?

• Is this use on-label or extra-label?

• What evidence supports this choice?

• Are there approved alternatives?

• What are the risks?

3. Ask whether it fits your horse’s joint problem

Adequan, Legend, Zycosan, corticosteroids, biologics, bisphosphonates, NSAIDs, and other therapies are not interchangeable.

The right choice depends on the diagnosis.

4. Consider competition rules

Medication rules vary by discipline, location, and governing body. Always ask your vet about withdrawal times and competition regulations before treatment.

5. Track response

Record:

• Lameness grade

• Warm-up time

• Stiffness

• Joint swelling

• Workload

• Farrier changes

• Medication dates

• Any reactions

• Performance changes

If a product is not helping, do not just repeat it because the bottle is popular.

Common Mistakes Owners Make

Calling Polyglycan “generic Adequan”

It is not. They are different products with different ingredients, routes, regulatory histories, and uses.

Choosing based on price alone

A cheaper product that does not treat the actual problem is not cheaper. It is just a more affordable way to delay a diagnosis.

Treating arthritis without confirming arthritis

Many lameness problems mimic joint disease.

Forgetting the foot

Hoof balance can make or break joint comfort. A horse with poor farriery may not respond well to joint medication until the mechanics are improved.

Repeating injections without reassessment

If lameness keeps returning quickly, the diagnosis or management plan needs review.

Ignoring injection risks

Any injection has risk. Intra-articular injection has special risk because joint infection can be serious.

Expecting one injection to fix a management problem

Arthritis care is usually multimodal. Medication may help, but weight, fitness, footing, farriery, workload, and recovery matter too.

How to Build a Better Arthritis Plan

A good equine arthritis plan should be practical and diagnosis-based.

It may include:

• Accurate lameness diagnosis

• Radiographs where appropriate

• Hoof balance and farrier review

• Weight management

• Controlled exercise

• Workload modification

• Warm-up and recovery planning

• Appropriate NSAID use when needed

• Approved systemic joint medications where appropriate

• Intra-articular treatment when indicated

• Monitoring for treatment response

• Rechecking if signs return

• Competition medication planning

• Avoiding unnecessary injections

The best treatment plan is not the one with the most products.

It is the one that matches the horse’s problem.

FAQs

Is Polyglycan the same as Adequan?

No. Adequan is PSGAG and is labelled for intramuscular use in horses. Polyglycan contains hyaluronic acid, chondroitin sulfate, and N-acetyl-D-glucosamine and is marketed around synovial fluid replacement or lavage. They are not generic equivalents.

Is Adequan FDA-approved for horses?

Yes. Adequan i.m. is approved by the FDA under NADA #140-901 and is recommended for intramuscular treatment of non-infectious degenerative or traumatic joint dysfunction and associated lameness of the carpal and hock joints in horses. (DailyMed)

Is Legend the same as Adequan?

No. Legend is hyaluronate sodium, while Adequan is PSGAG. Legend is labelled for treatment of joint dysfunction of the carpus or fetlock due to non-infectious synovitis associated with equine osteoarthritis. (DailyMed)

Can a horse use more than one joint therapy?

Sometimes, but only under veterinary direction. Combining products without a diagnosis can increase cost, risk, and confusion without improving the horse.

Should I use the cheaper joint injection?

Not without asking what it is, what it is approved for, what evidence supports it, how it will be used, and what risk it carries. Price matters, but it should not override diagnosis, safety, and evidence.

Final Thoughts

Adequan and Polyglycan should not be treated as interchangeable arthritis products.

Adequan is an FDA-approved intramuscular PSGAG medication with a specific equine label. Legend is an FDA-approved hyaluronate sodium product with its own label and use case. Zycosan is another FDA-approved injectable option for controlling clinical signs of osteoarthritis in horses. Polyglycan is a different combination product marketed around synovial fluid replacement, lavage, or viscosupplementation, and it should not be described to owners as generic Adequan.

The real question is not “Which bottle is cheaper?”

The real question is: what is wrong with this horse, what evidence supports this treatment, and is this the safest and most appropriate product for this case?

That is where your vet matters.

Good arthritis care is not product shopping. It is diagnosis, mechanics, medication, monitoring, and a long-term plan that keeps the horse as comfortable and functional as possible.

If you are unsure whether your horse needs Adequan, Legend, Polyglycan, Zycosan, joint injections, imaging, or a full lameness workup, ASK A VET™ can help you understand what questions to ask your veterinarian before starting treatment.