Can Horses Take Previcox Instead of Equioxx?

By Dr Duncan Houston

PREVICOX® and EQUIOXX® both contain firocoxib, so it is easy to understand why horse owners may assume they are interchangeable.

The confusion becomes even greater because one PREVICOX® tablet strength contains 57 mg of firocoxib, which is also the strength of the approved EQUIOXX® horse tablet. However, PREVICOX® is labelled for dogs, is also sold as a much larger 227 mg tablet, and carries canine dosing instructions that are dramatically different from equine dosing.

The practical answer is simple: do not give a horse PREVICOX® from a dog’s prescription unless the horse’s veterinarian has specifically prescribed and labelled it for that individual horse.

Quick Answer

PREVICOX® and EQUIOXX® contain the same active ingredient, firocoxib, but they are not owner-interchangeable products.

FDA-approved horse firocoxib products, including EQUIOXX® and approved equine generics, should normally be used for horses. Extra-label use of PREVICOX® may be lawful only under specific veterinarian-directed conditions, but using leftover dog medication or substituting it solely to save money is not an appropriate owner decision.

If your horse has accidentally received PREVICOX®, check whether the tablet was 57 mg or 227 mg, record how many tablets were given, and contact your veterinarian before administering anything else. The EQUIOXX® horse information sheet specifically warns against giving PREVICOX® to horses because dosing errors may cause serious adverse effects. (Animal Drugs at FDA)

What Are Previcox and Equioxx?

Both products contain firocoxib, a prescription non-steroidal anti-inflammatory drug, or NSAID.

Firocoxib is used to control pain and inflammation associated with osteoarthritis. It does not cure arthritis or repair damaged cartilage, but it may improve comfort, mobility and willingness to exercise while the underlying condition is managed. (Animal Drugs at FDA)

Feature	PREVICOX®	EQUIOXX® Tablets
Approved species	Dogs	Horses
Active ingredient	Firocoxib	Firocoxib
Tablet strengths	57 mg and 227 mg	57 mg
Labelled dog dose	5 mg/kg once daily	Not applicable
Labelled horse dose	Not approved for horses	One 57 mg tablet once daily for horses weighing 800 to 1,300 lb
Labelled horse treatment duration	None	Up to 14 days
Approved indication	Canine osteoarthritis and certain postoperative pain	Equine osteoarthritis
Owner substitution acceptable?	No	Use according to the veterinarian’s instructions

The canine dose is 5 mg/kg, while the approved equine oral paste dose is approximately 0.1 mg/kg. That is a roughly 50-fold difference in the labelled milligram-per-kilogram dosing instructions. The approved equine tablet label simplifies this to one 57 mg tablet for horses weighing 800 to 1,300 lb, once daily for no more than 14 days. (Animal Drugs at FDA)

Why Do People Think Previcox Can Be Used in Horses?

There are three main reasons.

The active ingredient is the same

Both products contain firocoxib. A 57 mg PREVICOX® tablet and a 57 mg EQUIOXX® tablet contain the same stated quantity of active ingredient.

That does not make the products automatically interchangeable by an owner. Species approval, labelling, dosing instructions, treatment duration, safety information and legal dispensing requirements still matter.

Previcox has historically been cheaper

Some owners have found canine firocoxib tablets less expensive than equine-labelled products.

Price, however, does not determine whether a medication can legally or safely be substituted. FDA-approved generic firocoxib tablets for horses are now available, giving veterinarians and owners an equine-approved alternative to the brand-name product. The FDA approved the first generic horse firocoxib tablet in 2022, and the current FDA Green Book lists additional approved equine firocoxib products. (U.S. Food and Drug Administration)

Some veterinarians used canine tablets before equine tablets became available

EQUIOXX® oral paste was approved for horses before an equine tablet formulation was available. Veterinarians sometimes used canine firocoxib tablets extra-label when there was no equivalent approved horse tablet.

The regulatory position became less straightforward once 57 mg horse tablets containing firocoxib were approved for the same equine osteoarthritis indication.

Is Previcox Illegal to Use in Horses?

The original claim that PREVICOX® use in horses is always illegal is too absolute.

The more accurate answer is:

• Owners cannot independently use or repurpose prescription PREVICOX® for a horse.

• Veterinarians may prescribe approved animal or human drugs extra-label under the Animal Medicinal Drug Use Clarification Act, known as AMDUCA, when all relevant conditions are met.

• Extra-label use must occur on the lawful order of a licensed veterinarian within a valid veterinarian-client-patient relationship.

• The treatment must be medically justified and used to protect the animal’s health.

• Required records, directions and prescription labelling must be provided.

• State veterinary and pharmacy laws may impose additional requirements. (U.S. Food and Drug Administration)

The important FDA restriction

FDA guidance states that extra-label use is generally limited when there is already an approved animal drug:

• labelled for the intended use,

• containing the same active ingredient,

• in the required dosage form and concentration,

unless the veterinarian has a clinical basis for finding that the approved product is ineffective for its intended use. This principle also applies to the extra-label use of animal drugs in non-food animals. (U.S. Food and Drug Administration)

Because FDA-approved 57 mg firocoxib tablets for horses exist for equine osteoarthritis, routinely prescribing the canine 57 mg product merely because it is cheaper is difficult to square with that federal framework.

Cost alone is not the same as the approved equine product being clinically ineffective.

Whether a particular prescription complies with federal and state law depends on the exact circumstances, the horse’s status, the veterinarian’s clinical rationale and applicable local rules. This article discusses United States federal law. Other countries have different medication and prescribing regulations.

Can a Veterinarian Ever Prescribe Previcox to a Horse?

Potentially, but it would need to be a genuine veterinarian-directed extra-label decision rather than an informal substitution.

The veterinarian would need to:

• Have a valid veterinarian-client-patient relationship

• Diagnose or evaluate the horse’s condition

• Decide that treatment is medically required

• Determine whether the approved equine product can appropriately treat the horse

• Provide an exact dose and treatment duration

• Dispense or prescribe the product with appropriate extra-label directions

• Maintain the required medical records

• Consider food-chain and competition requirements where relevant

The owner should never calculate the dose from the dog instructions, share tablets between animals or assume that a previous prescription for another horse remains appropriate.

Why the Dose Difference Matters

The greatest practical danger is not necessarily a mysterious inactive ingredient. It is dosing confusion.

PREVICOX® dog tablets are supplied in:

• 57 mg tablets

• 227 mg tablets

EQUIOXX® horse tablets contain:

• 57 mg per tablet

One 227 mg PREVICOX® tablet contains almost four times the active ingredient in one approved EQUIOXX® horse tablet. Following the canine instruction of 5 mg/kg in a horse would produce a vastly excessive equine dose. (Animal Drugs at FDA)

What if an average horse received one 57 mg Previcox tablet?

One 57 mg PREVICOX® tablet is not automatically a toxic firocoxib dose in an average adult horse.

The approved EQUIOXX® tablet dose is also 57 mg for horses weighing 800 to 1,300 lb. The concern is that the product was not prescribed for that horse, the horse may fall outside that weight range, other medication may already have been given, or repeated doses may be inappropriate. (Animal Drugs at FDA)

Contact the veterinarian before giving another dose.

What if the horse received a 227 mg tablet?

A 227 mg tablet contains approximately four times the active ingredient in the approved 57 mg equine tablet.

Contact an equine veterinarian promptly, even if the horse currently appears normal. Risk depends on:

• The horse’s body weight

• The number of tablets swallowed

• Whether previous doses were given

• Hydration status

• Kidney, liver or gastrointestinal health

• Other NSAIDs or corticosteroids being used

• The time since administration

Do not wait for signs of toxicity before reporting a known substantial dosing error.

What about ponies, miniature horses and foals?

A 57 mg tablet may be excessive for a small equid because the approved tablet label applies to horses weighing 800 to 1,300 lb.

Small horses require an individually calculated veterinary plan. The safety of EQUIOXX® tablets has also not been established in horses under one year of age. (Animal Drugs at FDA)

Is Previcox Formulation Itself Toxic to Horses?

There is no need to claim that every inactive ingredient in PREVICOX® is inherently poisonous to horses.

The stronger and more accurate concern is that:

• PREVICOX® has not been approved and labelled as the equine product

• It is sold in a potentially dangerous 227 mg strength

• Canine dosing instructions are dramatically different

• Owners may unintentionally combine it with other equine NSAIDs

• Use may occur without appropriate examination or monitoring

• FDA-approved horse formulations are available

The FDA-approved EQUIOXX® client information sheet directly tells owners not to give PREVICOX® tablets to horses because overdoses may occur and result in serious side effects. (Animal Drugs at FDA)

Is Firocoxib Safer Than Bute or Banamine?

Firocoxib is a coxib-class NSAID designed to target inflammatory pathways more selectively than some traditional NSAIDs. That does not make it harmless.

Serious adverse effects associated with equine firocoxib can occur with or without obvious warning. The approved horse information identifies potential problems involving:

• The mouth and facial skin

• The kidneys

• The gastrointestinal tract

• The liver

The most frequently highlighted equine findings include erosions or ulcers involving the tongue, lips, mouth and facial skin, together with kidney-related effects. (U.S. Food and Drug Administration)

Firocoxib should still be treated as a prescription NSAID requiring appropriate patient selection and monitoring.

Which Horses Need Extra Caution?

Tell the veterinarian before giving firocoxib if the horse:

• Has kidney or liver disease

• Has a history of gastrointestinal ulceration

• Is dehydrated

• Has reduced appetite or diarrhoea

• Is recovering from severe colic

• Is receiving another NSAID

• Is receiving systemic corticosteroids

• Has previously reacted to aspirin or another NSAID

• Is under one year old

• Is pregnant, lactating or intended for breeding

• May be intended for human food consumption

The approved EQUIOXX® tablet label states that safety has not been determined in horses under one year of age, breeding horses, pregnant mares or lactating mares. It is also not labelled for horses intended for human food consumption. (Animal Drugs at FDA)

Can Firocoxib Be Combined With Other Pain Medication?

Do not combine it with another NSAID unless the attending veterinarian has made a specific plan.

Potentially problematic combinations include:

• Phenylbutazone

• Flunixin meglumine

• Aspirin

• Diclofenac

• Ketoprofen

• Meloxicam

• Another firocoxib product

EQUIOXX® should also not be given with systemic corticosteroids such as dexamethasone, prednisolone or triamcinolone. Combining or rapidly switching these medications may increase gastrointestinal and renal risk. The appropriate transition period depends on the horse, the medications involved and the clinical situation, so it should be set by the veterinarian rather than guessed by the owner. (Animal Drugs at FDA)

Can Firocoxib Be Used Long Term?

The FDA-approved EQUIOXX® tablet label permits treatment once daily for up to 14 days.

Any longer course falls outside that approved tablet duration and therefore requires an individual veterinary decision. Longer-term use may be clinically appropriate in selected horses, but it should not become an automatic repeat prescription without reassessing:

• Whether the horse still needs the medication

• Whether the diagnosis is correct

• Whether pain is progressing

• Hydration and appetite

• Kidney and liver health

• Gastrointestinal signs

• Other medication and supplements

• Whether non-drug management can be improved

A veterinarian may recommend physical examinations and blood testing before or during ongoing NSAID therapy, particularly in older horses or those with concurrent medical conditions. (Animal Drugs at FDA)

How Worried Should You Be?

Low Risk

The horse:

• Has received equine-labelled firocoxib prescribed by its veterinarian

• Is within the intended weight range

• Is receiving the correct dose

• Is eating and drinking normally

• Is not receiving another NSAID or corticosteroid

• Has no concerning medical history

What to do: Continue according to the prescription and monitor appetite, manure, drinking, urination, behaviour and the mouth.

Moderate Risk

There is:

• Uncertainty about which firocoxib product was given

• Uncertainty about whether a dose was duplicated

• One 57 mg PREVICOX® tablet given to an average-sized adult horse

• A missed or partially swallowed dose

• A horse outside the approved tablet weight range

• No current signs of illness

What to do: Contact the prescribing veterinarian before the next dose. Do not automatically redose or switch products.

High Risk

The horse:

• Received a 227 mg PREVICOX® tablet

• Received several tablets

• Has been given repeated unprescribed doses

• Is a pony, miniature horse or young horse

• Is dehydrated or systemically unwell

• Is also receiving bute, Banamine, aspirin or corticosteroids

• Develops reduced appetite, mouth sores, diarrhoea or altered drinking and urination

What to do: Contact an equine veterinarian urgently on the same day. Keep the medication packaging available.

Critical

The horse develops:

• Severe or persistent colic

• Collapse or profound weakness

• Severe diarrhoea

• Marked depression

• Inability or refusal to eat or drink

• Very little or no urine

• Facial swelling or a severe allergic reaction

• Yellow gums or yellowing of the eyes

• Significant oral ulceration

• Rapid deterioration

What to do: Treat this as an emergency and obtain immediate veterinary assistance.

When Is This an Emergency?

Seek urgent veterinary care after firocoxib administration if your horse shows:

• Severe abdominal pain

• Repeated rolling or violent pawing

• Collapse or inability to stand

• Marked weakness

• Severe or persistent diarrhoea

• Major reduction in urine production

• Refusal of both food and water

• Extensive sores or ulceration inside the mouth

• Facial swelling or breathing difficulty

• Yellow gums, skin or eyes

• Sudden neurological abnormalities

• A substantial known overdose

• Accidental administration alongside another NSAID or corticosteroid followed by illness

Serious NSAID effects may develop without much warning, so do not wait for several symptoms to appear when a significant overdose or dangerous drug combination is already known. (Animal Drugs at FDA)

What Should You Do If Your Horse Has Already Received Previcox?

1. Identify the exact product

Check the bottle or blister pack for:

• PREVICOX® or another canine firocoxib product

• 57 mg or 227 mg

• Number of tablets missing

• Expiry date

• Time of administration

Do not rely on the colour or size of a loose tablet.

2. Record the horse’s current weight

Provide the veterinarian with the most accurate recent weight available.

A miniature horse, pony and 600 kg Warmblood cannot be assessed using the same assumption.

3. List every other medication

Include:

• Phenylbutazone

• Flunixin

• Aspirin

• Meloxicam

• Diclofenac

• Dexamethasone

• Prednisolone

• Joint medication

• Ulcer medication

• Supplements

• Any recent injectable treatment

Do not assume an over-the-counter product is irrelevant.

4. Do not give another pain medication

Do not give the next firocoxib dose or another NSAID while waiting for advice.

If the horse is receiving a prescribed corticosteroid, tell the veterinarian immediately. Do not abruptly alter a prolonged corticosteroid course without professional direction.

5. Contact the veterinarian

Provide:

• Product name

• Tablet strength

• Number administered

• Horse’s weight

• Time given

• Previous doses

• Medical history

• Other medication

• Current signs

A known 227 mg dose or several tablets warrants a prompt call even when the horse appears normal.

6. Monitor the horse closely

Watch for:

• Appetite

• Water intake

• Manure quantity and consistency

• Urination frequency

• Colic signs

• Depression

• Oral sores

• Facial skin irritation

• Yellow mucous membranes

• Behavioural change

Do not administer oils, activated charcoal, gastrointestinal medication or intravenous fluids without veterinary direction.

7. Keep the packaging

The veterinarian may need the product name, strength, lot number and manufacturer information.

How Will the Veterinarian Assess the Risk?

The assessment begins with the amount of firocoxib received relative to the horse’s weight.

The veterinarian will also consider:

• Whether the horse was already receiving firocoxib

• Other NSAID or corticosteroid exposure

• Hydration

• Kidney and liver history

• Previous colic or gastrointestinal ulceration

• Age and body condition

• Current appetite and manure

• Time since administration

• Any emerging clinical signs

Depending on the situation, the horse may require:

• Physical examination

• Oral examination

• Kidney and liver blood testing

• Electrolyte assessment

• Complete blood count

• Urinalysis

• Fluid therapy

• Gastrointestinal support

• Serial monitoring

A normal horse immediately after an overdose is reassuring, but it does not completely rule out a delayed adverse effect.

Will My Horse Be Okay?

Most average-sized adult horses that accidentally receive a single 57 mg tablet and remain bright, eating and comfortable are unlikely to have received a dramatically excessive amount of active firocoxib, because 57 mg is also the approved EQUIOXX® tablet strength for many adult horses.

That does not mean owners should continue giving the canine product. The veterinarian still needs to confirm the horse’s weight, medical history, other medication and intended treatment duration. (Animal Drugs at FDA)

The outlook becomes more concerning when:

• A 227 mg tablet was given

• More than one tablet was swallowed

• Doses were repeated

• The horse is small

• Another NSAID or corticosteroid was also administered

• The horse is dehydrated

• Kidney, liver or gastrointestinal disease is present

• Clinical signs develop

Early veterinary advice gives the best opportunity to monitor and support the horse before significant complications appear.

What About Competition Horses?

A legal veterinary prescription does not automatically mean a horse is eligible to compete while receiving the medication.

Firocoxib is listed as a Controlled Medication under the 2026 FEI Equine Prohibited Substances List. USEF also maintains specific firocoxib treatment and withdrawal guidance, including restrictions on treatment duration. Rules differ between organisations and may change. (FEI Inside)

Before competition:

• Tell the veterinarian which organisation governs the event

• Check the current medication rules

• Record the last dose accurately

• Do not rely on an old withdrawal chart

• Remember that detection time and recommended withdrawal time are not necessarily the same

Changing from EQUIOXX® to PREVICOX® does not make firocoxib invisible to medication testing. The active ingredient remains firocoxib.

How Can Owners Reduce the Cost Safely?

Do not solve a price problem by using another animal’s prescription.

Instead, ask the veterinarian about:

• FDA-approved generic firocoxib tablets for horses

• Whether oral paste or tablets are more suitable

• Whether firocoxib remains necessary

• The shortest effective treatment period

• Reassessment of the underlying source of pain

• Alternative approved treatment plans

• Pharmacy price comparisons for the prescribed equine product

The presence of approved generic horse tablets means the choice is no longer simply expensive EQUIOXX® or cheaper dog medication. (U.S. Food and Drug Administration)

What Else Should Be Included in an Arthritis Plan?

Medication should not be the entire plan.

Long-term osteoarthritis management may also involve:

• Confirming which joint or structure is painful

• Weight and body condition management

• Regular controlled exercise

• Appropriate warm-up and recovery

• Hoof balance and farrier care

• Suitable footing

• Saddle assessment

• Rehabilitation

• Joint-specific treatment where indicated

• Monitoring changes in performance and mobility

The mistake is using an NSAID to keep the horse working while never investigating why the horse requires daily pain relief.

A horse needing progressively more medication, becoming increasingly stiff or losing performance deserves reassessment rather than a larger supply of tablets.

Common Mistakes Owners Make

Assuming the same active ingredient means the products are interchangeable

The active molecule may be the same, but the approved species, tablet strengths, label dose and legal directions differ.

Following the dog dose for a horse

The canine labelled dose is approximately 50 times the equine labelled dose on a milligram-per-kilogram basis.

Giving a 227 mg tablet without checking the strength

The larger canine tablet contains almost four times the active ingredient in the approved 57 mg equine tablet.

Combining firocoxib with bute or Banamine

Stacking NSAIDs can increase gastrointestinal and kidney risk.

Using leftover medication

A previous prescription belongs to the animal and condition for which it was prescribed.

Continuing beyond 14 days without review

The approved EQUIOXX® tablet duration is up to 14 days. Longer treatment requires veterinary oversight.

Assuming a selective NSAID cannot cause ulcers or kidney injury

Firocoxib may be more selective, but serious adverse effects remain possible.

Treating the price difference as a legal exception

Cost alone does not establish that the approved equine drug is clinically ineffective.

Ignoring competition rules

Prescription medication may still be prohibited or restricted during competition.

How Can Medication Errors Be Prevented?

• Store dog and horse medication separately

• Keep tablets in their original labelled containers

• Write the horse’s name and dose clearly

• Record every dose immediately

• Have one person responsible for medication

• Check the strength before every dose

• Never estimate from tablet colour or size

• Tell the veterinarian about all NSAIDs and corticosteroids

• Dispose of outdated medication appropriately

• Review repeat prescriptions rather than allowing indefinite automatic refills

A simple medication log can prevent double dosing when several staff members care for the same horse.

Frequently Asked Questions

Are Previcox and Equioxx the same medication?

They contain the same active ingredient, firocoxib. They are different approved products with different species labels, strengths, instructions and safety information.

Can my veterinarian legally prescribe Previcox to my horse?

Extra-label prescribing may be lawful under limited veterinarian-directed circumstances. However, FDA-approved equine firocoxib tablets are available, and federal rules restrict extra-label use when an approved product with the same active ingredient in the required form and concentration already exists and is clinically effective.

My horse received one 57 mg Previcox tablet. Is that an overdose?

Not necessarily in an average adult horse. The approved EQUIOXX® horse tablet also contains 57 mg for horses weighing 800 to 1,300 lb. Contact your veterinarian before giving another dose, particularly if the horse is small, unwell or receiving other medication.

What should I do if my horse received a 227 mg Previcox tablet?

Call an equine veterinarian promptly. A 227 mg tablet contains almost four times the firocoxib in the approved 57 mg equine tablet. Do not administer another NSAID while waiting for advice.

Can my horse take firocoxib for longer than 14 days?

The approved EQUIOXX® tablet label limits treatment to 14 days. Longer use is extra-label and should occur only under veterinary supervision, with reassessment and monitoring appropriate to the individual horse.

The Real Takeaway

PREVICOX® and EQUIOXX® contain the same active drug, but that does not turn a dog prescription into an owner-approved horse prescription.

The biggest risks are incorrect tablet strength, use of canine dosing instructions, combining NSAIDs, overlooking medical risk factors and continuing treatment without monitoring. The FDA-approved horse information specifically warns owners not to give PREVICOX® to horses because dosing errors may cause serious adverse effects.

The legal position is also more nuanced than saying PREVICOX® is always illegal in horses. Veterinarians have authority to prescribe medications extra-label under defined conditions, but routine cost-driven substitution is not the purpose of that authority when approved equine firocoxib products are available.

Use an approved horse product whenever appropriate, ask about equine generics when cost is a concern, and never share prescription medication between animals without direct veterinary instructions.

---

Unsure whether your horse has received the correct firocoxib product or dose? ASK A VET™ can help you organise the product strength, amount given, medication history and current symptoms so you can understand the urgency. A known overdose, severe colic, collapse or serious adverse reaction requires immediate contact with an on-site equine veterinarian.