Equioxx is an FDA-approved anti-inflammatory pain medication for horses, specifically designed to treat the pain and inflammation caused by osteoarthritis. It contains the active ingredient firocoxib, given once daily as either a tablet or oral paste. If your vet has mentioned Equioxx or you’re exploring options for a horse with joint pain, here’s what you need to know about how it works, how it’s given, and what to watch for.
How Equioxx Works
Equioxx belongs to a class of drugs called NSAIDs (non-steroidal anti-inflammatory drugs), similar in concept to ibuprofen in humans but formulated specifically for horses. It reduces pain, inflammation, and fever by targeting an enzyme called COX-2, which is one of the key triggers of the inflammatory response in the body.
What makes firocoxib different from older horse NSAIDs is its selectivity. The body has two versions of the COX enzyme. COX-1 handles protective housekeeping functions like maintaining the stomach lining and supporting kidney blood flow. COX-2 ramps up during injury or disease and drives pain and swelling. Firocoxib preferentially blocks COX-2 while leaving COX-1 relatively alone, which in theory means it controls pain with less risk to the stomach and kidneys than less selective NSAIDs. That said, the FDA notes that the real-world significance of this selectivity hasn’t been fully established, so side effects are still possible.
What Equioxx Treats
Equioxx is FDA-approved for one specific condition: pain and inflammation associated with osteoarthritis in horses. Osteoarthritis is extremely common in performance horses and aging horses alike, causing chronic joint stiffness, swelling, and lameness. For horses dealing with this kind of ongoing joint deterioration, Equioxx can make a meaningful difference in comfort and mobility.
Veterinarians sometimes use Equioxx for other sources of musculoskeletal pain as well, though its formal approval is limited to osteoarthritis. Your vet will determine whether it’s the right fit based on your horse’s specific condition.
Forms, Dosing, and Duration
Equioxx comes in two forms:
- Tablets: 57 mg scored tablets, designed for horses weighing 800 to 1,300 pounds. One tablet is given by mouth once daily.
- Oral paste: Administered in a syringe like a dewormer, dosed at 0.045 mg per pound of body weight (0.1 mg/kg), once daily.
Both forms are approved for use up to 14 consecutive days. This is an important limit. If your horse needs longer-term pain management, that’s a conversation with your veterinarian about whether continued use is appropriate and how to monitor for problems. There is no loading dose required, so the standard daily amount starts on day one.
Side Effects to Watch For
The most common side effects involve the mouth, face, and kidneys. Specifically, watch for:
- Sores or ulcers on the tongue or inside the mouth
- Scabs, redness, or rubbing around the facial skin, particularly near the mouth
- Changes in eating or drinking habits, either how often or how much
- Changes in urination, including frequency or color
Gastrointestinal and liver problems have also been reported with NSAIDs in general. If your horse stops eating, seems unusually lethargic, develops diarrhea, or shows any of the oral or facial signs listed above, stop giving Equioxx and contact your vet. These reactions can develop at any point during treatment, so daily observation matters even if your horse tolerated the first several doses without issue.
Important Safety Considerations
Equioxx should not be combined with other NSAIDs (like phenylbutazone) or with corticosteroids. Stacking anti-inflammatory drugs dramatically increases the risk of stomach ulcers, kidney damage, and other serious complications. If your horse is transitioning from another NSAID to Equioxx, your vet will typically build in a washout period between the two medications.
Horses with pre-existing kidney, liver, or gastrointestinal problems are at higher risk for adverse reactions. The same applies to horses that are dehydrated or in poor overall condition. Making sure your horse has consistent access to fresh water and forage during treatment helps support kidney function and gut health.
Equioxx vs. Previcox
You may have heard that Previcox, a firocoxib product made for dogs, contains the exact same active ingredient as Equioxx at a much lower price. This is true on a milligram-for-milligram basis. However, it is illegal for a veterinarian to prescribe Previcox for a horse because an equine-approved version of the same drug already exists. FDA regulations require vets to use the species-approved product when one is available.
The cost difference tempts some horse owners, but the legal and practical risks are real. If a horse has an adverse reaction to Previcox prescribed off-label, the drug manufacturer will not stand behind the veterinarian. The vet’s malpractice insurance also won’t cover the situation because the prescription was written illegally. In extreme cases, the FDA can pursue federal action against the prescribing veterinarian. A generic firocoxib tablet for horses was approved by the FDA, which may offer some cost savings over the brand-name Equioxx while staying within legal boundaries.