Firocoxib, marketed as Equioxx for horses, is a COX-2 selective (coxib-class) nonsteroidal anti-inflammatory drug approved by the FDA for the control of pain and inflammation associated with osteoarthritis in horses. It is the first and only COX-2 selective NSAID approved specifically for equine use. Its selectivity for COX-2 over COX-1 is intended to provide anti-inflammatory and analgesic effects while reducing the gastrointestinal side effects associated with traditional non-selective NSAIDs like phenylbutazone and flunixin meglumine.
Overview
Firocoxib preferentially inhibits cyclooxygenase-2 (COX-2), the enzyme primarily responsible for producing prostaglandins that mediate pain and inflammation. By sparing COX-1 to a greater degree, firocoxib is expected to have less impact on the protective prostaglandins that maintain gastrointestinal mucosal integrity and renal blood flow. However, COX-2 selectivity does not eliminate GI risk entirely, and horses on firocoxib should still be monitored for adverse effects.
Uses
- Osteoarthritis (OA) — FDA-approved indication for control of pain and inflammation
- Degenerative joint disease — management of chronic joint pain
- Musculoskeletal lameness — where prolonged NSAID therapy may be needed
- Post-operative orthopedic pain — under veterinary direction
Firocoxib is particularly useful when longer-term NSAID therapy is anticipated because its COX-2 selectivity may offer a better GI safety margin compared to phenylbutazone or flunixin for extended use.
Dosage
Follow your veterinarian’s instructions. The FDA-approved dosing for horses:
| Formulation | Dose | Route | Frequency | Duration |
|---|---|---|---|---|
| Equioxx oral paste | 0.1 mg/kg (45.5 mg per 454 kg horse) | Oral | Once daily | Up to 14 days (FDA label) |
| Equioxx tablets | 0.1 mg/kg | Oral | Once daily | As directed |
Equioxx is available as an oral paste syringe and as tablets. The equine formulation (Equioxx) should always be used for horses rather than the canine product (Previcox), even though both contain firocoxib, because the equine product is formulated and dosed appropriately for horses.
Some veterinarians prescribe firocoxib for longer than the 14-day FDA-labeled duration under their clinical judgment. Discuss extended use risks and monitoring with your veterinarian.
Side Effects
| Common | Serious (Contact Your Vet) |
|---|---|
| Mild appetite reduction | GI ulceration (less frequent than with non-selective NSAIDs but still possible) |
| Soft stool | Right dorsal colitis (rare but reported) |
| Weight loss with prolonged use | Kidney impairment |
| Oral ulceration | |
| Hepatotoxicity (rare) |
While firocoxib has a more favorable GI safety profile than phenylbutazone or flunixin in clinical studies, it is not risk-free. Right dorsal colitis and gastric ulceration have been documented with firocoxib use, particularly with higher-than-labeled doses, prolonged duration, or concurrent risk factors.
Drug Interactions
- Other NSAIDs: Never combine firocoxib with phenylbutazone, flunixin, or any other NSAID. Allow at least a 24-hour washout when switching.
- Corticosteroids: Concurrent use increases GI ulceration risk significantly.
- Aminoglycoside antibiotics: Potential for additive nephrotoxicity.
- Other protein-bound drugs: Firocoxib is highly protein-bound and may interact with other highly bound drugs.
Contraindications
- Horses with known GI ulceration or right dorsal colitis
- Horses with kidney or liver disease
- Dehydrated horses
- Horses receiving another NSAID or systemic corticosteroid
- Known hypersensitivity to firocoxib
- Breeding stallions and mares (reproductive safety not established)
Storage
- Store at controlled room temperature, 59-86 degrees F (15-30 degrees C).
- Keep in original packaging to protect from moisture.
- Keep out of reach of children and animals.
Frequently Asked Questions
Is Equioxx safer than bute for long-term use? Clinical studies suggest firocoxib causes fewer GI side effects than phenylbutazone at labeled doses over 14 days. However, no NSAID is without risk for prolonged use. Your veterinarian will help determine the best option.
Can I use Previcox (the dog version) for my horse? While both products contain firocoxib, always use the equine-labeled product (Equioxx). Dosing differs between species, and using off-label products may affect your horse’s safety and your regulatory compliance.
Does Equioxx affect drug testing in competition horses? Yes. Firocoxib is a regulated substance under FEI, USEF, and racing commission rules. Consult your veterinarian and competition governing body for withdrawal guidelines.
Can I give Equioxx with GastroGard (omeprazole)? Many veterinarians co-prescribe omeprazole to protect against gastric ulceration during NSAID therapy. Omeprazole does not protect against right dorsal colitis. Discuss gastroprotective strategies with your veterinarian.
This information is for educational purposes only and does not replace professional veterinary advice. Always consult your veterinarian before administering any medication to your horse.