Firocoxib
3-(cyclopropylmethoxy)-5,5-dimethyl-4-(4-methylsulfonyl) phenylfuran-2(5H)-one
Also known as: Previcox · Equioxx · ML-1,785,713 · Firocoxibum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Control of pain and inflammation associated with osteoarthritis | 5 mg/kg (2.27 mg/lb) | PO | once daily | — | 🌎 NA |
| Pain and inflammation (osteoarthritis, surgery) | 5 mg/kg | PO | q24h | As directed (monitor carefully if >90 days) | 🌍 EU |
- Control of pain and inflammation associated with osteoarthritis: Dosage should be calculated in half tablet increments and can be administered with or without food.
- Pain and inflammation (osteoarthritis, surgery): Give with or without food. For perioperative pain, give the first dose 2 hours before surgery.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Experimentally induced pyrexia (Unapproved/Investigational) | 0.75-3 mg/kg | PO | single dose | single dose | 🌎 NA |
| Contraindicated | Do not use | PO | N/A | N/A | 🌍 EU |
- Experimentally induced pyrexia (Unapproved/Investigational): Caution: While firocoxib may ultimately be shown to be safe for use in cats, supporting information (or FDA approval) is not currently available for it to be recommended.
- Contraindicated: Strictly contraindicated in cats.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Control of pain and inflammation associated with osteoarthritis | 0.1 mg/kg (0.045 mg/lb) body weight | PO | daily | up to 14 days | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Firocoxib is a highly selective nonsteroidal anti-inflammatory drug (NSAID) belonging to the coxib class.
- Primary Use: Management of pain and inflammation associated with osteoarthritis in dogs and horses.
- Surgical Use: Control of postoperative pain and inflammation associated with orthopedic surgery in dogs.
- Clinical Pearl: As a COX-2 selective inhibitor, it is designed to provide robust analgesia while minimizing the gastrointestinal and renal side effects commonly seen with non-selective NSAIDs. Interestingly, firocoxib has also demonstrated potential anti-tumor activity, particularly in COX-2 expressing neoplasms, and may have a role in veterinary oncology.
Mechanism of action
Firocoxib exerts its analgesic, antipyretic, and anti-inflammatory effects by selectively inhibiting the cyclooxygenase-2 (COX-2) enzyme.
- Cellular Membrane Phospholipids → Arachidonic Acid → COX-2 → Pro-inflammatory Prostaglandins (e.g., PGE2).
- By blocking this pathway, firocoxib reduces vasodilation, tissue edema, and sensitization of nociceptors.
- COX-1 Sparing: At therapeutic doses, it predominantly spares the COX-1 enzyme, which is constitutively expressed and responsible for synthesizing cytoprotective prostaglandins that maintain gastrointestinal mucosal integrity, renal blood flow, and platelet function.
Safety & warnings
Contraindications
- Hypersensitivity to firocoxib or other NSAIDs
- Active GI ulcerative conditions (relative contraindication)
- Bleeding disorders or thrombocytopenia (relative contraindication)
- Dogs weighing less than 7 lbs
- Puppies less than 7 months old (US labeling) or less than 10 weeks old (UK labeling)
- Horses less than 1 year old
- Breeding, pregnant, or lactating dogs or horses (safety not established)
- Cats
- Dogs < 10 weeks of age or < 3 kg body weight
- Pregnant or lactating bitches
- Dehydrated, hypovolaemic, or hypotensive patients
- Patients with pre-existing gastrointestinal disease or bleeding
- Patients with blood clotting disorders
Adverse effects
- Dogs: Vomiting, decreased appetite/anorexia, diarrhea, melena, GI ulcers, bloody vomiting, GI perforation
- Dogs: Increases in BUN, creatinine, alkaline phosphatase (ALP), and ALT
- Dogs: Depression/lethargy, ataxia
- Horses: Diarrhea/loose stools, mouth ulcers, facial skin lesions, excitation (rare)
- Gastrointestinal signs (vomiting, diarrhea, inappetence)
- Gastrointestinal ulceration or bleeding
- Renal toxicity (especially during hypotensive states)
- Hepatotoxicity (rare, but liver disease prolongs metabolism)
Precautions
Important Washout Period: If changing from one NSAID to another, a washout period is required. A 24-hour washout is often recommended between COX-2 selective agents, but 72 hours to 1 week is usually recommended when switching from a non-selective NSAID or aspirin.
- Use with caution and enhanced monitoring in patients with pre-existing renal, hepatic, or cardiovascular dysfunction.
- Use with caution in patients that are dehydrated, hypovolemic, hypotensive, or on concomitant diuretic therapy due to increased risk of renal toxicity.
- Geriatric patients require ongoing monitoring due to naturally reduced renal function.
- Puppy Toxicity: Doses above the recommended 5 mg/kg in puppies less than 7 months old have been associated with serious adverse reactions, including hepatic fatty changes and death.
Drug interactions
Some NSAIDs can reduce effects on blood pressure
May increase the risk of gastrointestinal toxicity (ulceration, bleeding, vomiting, diarrhea)
May increase the risk of gastrointestinal toxicity (ulceration, bleeding, vomiting, diarrhea)
NSAIDs may increase serum levels
Administration has increased plasma levels of celecoxib in humans and potentially could also affect firocoxib levels in dogs
NSAIDs may reduce the saluretic and diuretic effects
May displace other highly bound drugs or be displaced by them, potentially increasing serum levels, duration of action, and toxicity
Serious toxicity has occurred when NSAIDs have been used concomitantly; use together with extreme caution
May enhance the risk of nephrotoxicity development
Increased risk of severe gastrointestinal ulceration and renal toxicity. A 3-5 day wash-out period is required.
Synergistic gastrointestinal toxicity leading to severe ulceration or perforation.
Increased risk of nephrotoxicity.
Potential synergistic efficacy in treating transitional cell carcinomas.
Increased risk of gastrointestinal ulceration and bleeding.
Increased risk of nephrotoxicity.
Monitoring
- Baseline and periodic physical exam including clinical efficacy and adverse effect queries
- Baseline and periodic CBC
- Baseline and periodic liver function tests
- Baseline and periodic renal function tests and electrolytes
- Baseline and periodic urinalysis
- Clinical signs of GI toxicity (vomiting, diarrhea, melena, anorexia)
- Renal parameters (BUN, Creatinine, USG) especially in older dogs or long-term use
- Hepatic enzymes (ALT, ALP, Bilirubin) prior to and during long-term therapy
- Hydration status and blood pressure (especially perioperatively)
Pharmacokinetics
Half-life
Absorption
Dogs: Oral bioavailability is ~38% (chewable tablets). Food delays but does not affect the amount absorbed. Peak levels occur at 1 hour (fasted) or 5 hours (fed). Horses: Oral bioavailability is ~79% (paste). Peak levels occur 4-12 hours post-dose. Cats: Oral bioavailability is ~60% (suspension).
Distribution
Dogs: Vd is ~3 L/kg; 96% bound to plasma proteins. Horses: Vd is 1.7-2.3 L/kg; 98% bound to plasma proteins. Cats: Vd is 2-3 L/kg.
Metabolism
Dogs: Biotransformation occurs predominantly via dealkylation and glucuronidation in the liver. Horses: Biotransformation occurs primarily via decyclopropylmethylation and then glucuronidation.
Elimination
Dogs: Elimination is principally in the bile and feces. Horses: Metabolites are primarily excreted in the urine.
Overdose
Limited information is available for acute overdoses in animals. The reported oral LD50 for rats is > 2 grams per kg.
- Management: Should an overdose occur, contacting an animal poison control center or the manufacturer is highly recommended.
- Treatment: Use of gut emptying protocols and supportive treatment (IV fluids, oral sucralfate, GI protectants) may be useful in managing the case.
Available products
Formulations
- Chewable tablets
- Oral paste
- 57 mg oral tablet
- 227 mg oral tablet
Veterinary
- Firocoxib Chewable Tablets (scored): 57 mg & 227 mg; Previcox (Merial)
- Firocoxib Oral Paste: 0.82% w/w (8.2 mg firocoxib per gram of paste) in a 6.93 gram oral syringe; Equioxx (Merial)
- Previcox 57 mg chewable tablets
- Previcox 227 mg chewable tablets
Regulatory status
POM-V classification.
POM-V classification.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Commercially available tablets and oral paste should be stored at room temperature (15-30°C); brief excursions are permitted up to 40°C (104°F).
Client information
- Administration: Can be given with or without food. If stomach upset occurs, giving it with a meal may help.
- What to Watch For (Dogs): Stop the medication and contact your veterinarian immediately if you notice vomiting, decreased appetite/weight loss, diarrhea or loose stools, changes in behavior or activity, changes in water consumption or urination, or yellowing of the whites of eyes or mucous membranes (jaundice).
- What to Watch For (Horses): Contact your veterinarian if the patient develops ulcers or sores on the tongue or in the mouth, sores or lesions on facial skin or lips, diarrhea/loose stools, or changes in feed/water consumption.
-
Safety Warning: NEVER give your pet human pain relievers (like Advil, Tylenol, or Aspirin) or other veterinary NSAIDs while they are taking firocoxib, as this can cause fatal stomach ulcers or kidney failure.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.