Equioxx vs Previcox in Horses: What Horse Owners Need to Know

By Dr Duncan Houston

If you have ever compared Equioxx and Previcox, you have probably noticed the obvious catch: they both contain firocoxib. That is where the confusion starts. Owners then quite reasonably ask why one product is used in horses and the other is labeled for dogs, and whether the cheaper dog product can just be substituted.

Here is the important update: this is no longer just a simple price conversation. Equioxx is an FDA-approved horse product, and there are now FDA-approved firocoxib tablets for horses, including generic options, so the old shortcut logic around using Previcox in horses is even weaker than it used to be. The horse label also specifically warns: do not give Previcox chewable tablets for dogs to horses, as overdoses may occur and result in serious side effects. (U.S. Food and Drug Administration)

Quick Answer

Equioxx and Previcox both contain firocoxib, but Equioxx is labeled for horses and Previcox is labeled for dogs. For horses, the correct products are Equioxx oral paste, Equioxx tablets, Equioxx injection, or approved generic firocoxib tablets for horses. Using Previcox dog chewables in horses is not appropriate because the horse labeling specifically warns against it due to overdose risk and potential serious side effects. (animaldrugsatfda.fda.gov)

Are Equioxx and Previcox the same drug?

At the active ingredient level, yes. Both contain firocoxib, a COX-2 selective non-steroidal anti-inflammatory drug used to control pain and inflammation. But that does not make the products interchangeable. What matters clinically is the species label, formulation, dosing, and safety instructions attached to the product. FDA-approved NSAID labels are written for the specific species they are approved for, and that is part of how safe use is defined. (U.S. Food and Drug Administration)

What is Equioxx approved for in horses?

Equioxx is approved in horses for control of pain and inflammation associated with osteoarthritis. In the US, approved equine firocoxib products include:

• Equioxx Oral Paste

• Equioxx Tablets

• Equioxx Injection

• generic firocoxib tablets for horses approved by the FDA (animaldrugsatfda.fda.gov)

That is a big practical point. This is not a situation where there is no horse-specific option available. There are multiple horse-specific options now.

What is Previcox approved for?

Previcox is approved for dogs, not horses. FDA approval for dog firocoxib products covers use such as control of pain and inflammation associated with osteoarthritis and postoperative pain and inflammation in dogs. The dog label is a dog label for a reason. (animaldrugsatfda.fda.gov)

Why is using Previcox in horses a bad idea?

The clearest answer comes straight from the horse firocoxib labeling: do not give Previcox chewable tablets for dogs to horses, as overdoses may occur and result in serious side effects. (animaldrugsatfda.fda.gov)

That warning matters because this is not just regulatory paperwork. It reflects real-world safety issues:

• the dog product is formulated and labeled for dogs

• the chewable format can encourage inaccurate dosing in horses

• the dose exposure can be wrong for the horse

• side effect risk rises when dosing is wrong, especially with NSAIDs that can affect the gastrointestinal tract and kidneys (animaldrugsatfda.fda.gov)

In practical terms, this is one of those cases where “same ingredient” does not mean “same product choice.”

Severity framework: how worried should you be?

Low concern

Your horse is already on an approved horse firocoxib product such as Equioxx or an FDA-approved generic horse tablet, and dosing is being followed correctly.

What this usually means:

• you are using the right type of product

• normal NSAID monitoring still matters

• ongoing vet oversight is still a good idea for long-term use (animaldrugsatfda.fda.gov)

Moderate concern

Your horse owner group, barn contact, or online forum has suggested using Previcox because it is “basically the same thing.”

What this means:

• the advice is oversimplified

• the horse-specific warning is being ignored

• you should not switch products casually (animaldrugsatfda.fda.gov)

High concern

A horse has already been given Previcox dog tablets, or someone is trying to substitute it without veterinary guidance.

What this means:

• there is dosing and safety risk

• the horse should be monitored for NSAID adverse effects

• your vet should be contacted for case-specific advice (animaldrugsatfda.fda.gov)

When is this an emergency?

Seek veterinary advice urgently if a horse given any NSAID develops:

• reduced appetite

• colic signs

• diarrhea

• marked lethargy

• dehydration

• reduced urination

• worsening illness after dosing

NSAID adverse effects in horses can involve the gastrointestinal tract and kidneys, and the risk is more concerning when the wrong product or wrong dose has been used. (U.S. Food and Drug Administration)

Is Equioxx safer just because it is more expensive?

Not because it is more expensive. Because it is the product labeled for horses, with horse-specific dosing and safety instructions. That is the real point.

And this is where the old price argument has aged badly. There are now FDA-approved generic firocoxib tablets for horses, so owners looking for a more economical route have horse-labeled alternatives that do not require reaching for a dog chewable product. (U.S. Food and Drug Administration)

What should you do next?

If your horse needs firocoxib, the sensible plan is:

1. Use a horse-labeled product

That means Equioxx paste, Equioxx tablets, Equioxx injection, or an approved generic horse tablet. (animaldrugsatfda.fda.gov)

2. Do not substitute Previcox dog tablets

The horse label explicitly warns against it. (animaldrugsatfda.fda.gov)

3. Ask about the most practical horse option

Some horses do better with paste, some with tablets, and some situations call for injectable treatment under veterinary supervision. (animaldrugsatfda.fda.gov)

4. Monitor like any NSAID case

Appetite, comfort, manure, hydration, and overall attitude still matter.

Common mistakes

Assuming same ingredient means interchangeable

It does not.

Treating this as a cost-only issue

It is a dosing and safety issue too.

Using old barn advice from before horse tablets were widely available

There are now approved horse tablet options, including generics. (U.S. Food and Drug Administration)

Forgetting that labels are species-specific for a reason

That is especially true with NSAIDs. (U.S. Food and Drug Administration)

FAQ

Do Equioxx and Previcox contain the same active ingredient?

Yes. Both contain firocoxib. (animaldrugsatfda.fda.gov)

Is Previcox approved for horses?

No. It is approved for dogs. (animaldrugsatfda.fda.gov)

Can horses get firocoxib tablets now without using dog tablets?

Yes. FDA-approved firocoxib tablets for horses, including generic products, are available. (U.S. Food and Drug Administration)

Why does the horse label warn against Previcox?

Because overdoses may occur and result in serious side effects if the dog chewable product is given to horses. (animaldrugsatfda.fda.gov)

Is Equioxx only available as paste?

No. In the US there are approved oral paste, tablet, and injectable forms, plus approved generic horse tablets. (animaldrugsatfda.fda.gov)

Final thoughts

The real takeaway is simple. This is not a debate about whether firocoxib works in horses. It does. The question is which product should be used.

For horses, use the horse-approved firocoxib products. That is the safest, cleanest, and most defensible choice. The old idea of substituting Previcox because it shares the same active ingredient does not hold up well once you factor in the horse-specific warning, overdose risk, and the fact that approved horse tablet options now exist.

If you want help understanding whether your horse’s pain plan is appropriate, or what to monitor while using an NSAID, ASK A VET™ can help you work through the practical next steps.