Firocoxib

NSAID Coxib (selective COX-2 inhibitor)

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog Oral 5 mg/kg Once daily (q24h) Duration: For osteoarthritis: up to 30 days; for postoperative pain: 3-7 days
Notes: Administer with food to reduce GI upset. Doses should be adjusted for body weight. Safety has not been established beyond 30 days.
Horse Oral 0.1 mg/kg Once daily (q24h) Duration: For osteoarthritis: up to 14 days; for postoperative pain: 3-7 days
Notes: Administer as oral paste. Do not exceed 14 days of continuous therapy. Monitor for GI and renal effects.

Clinical Indications & Species Uses

General Indications
  • Pain and inflammation associated with musculoskeletal disorders
  • Postoperative pain management
Dog (Canine)
  • Control of pain and inflammation associated with osteoarthritis
  • Control of postoperative pain and inflammation associated with soft tissue and orthopedic surgery
Horse (Equine)
  • Control of pain and inflammation associated with osteoarthritis
  • Control of pain and inflammation associated with soft tissue and orthopedic surgery

Pharmacology & Mechanism of Action

Drug Class: NSAID | Pharmacological Group: Coxib (selective COX-2 inhibitor)

Mechanism of Action: Firocoxib is a nonsteroidal anti-inflammatory drug (NSAID) that selectively inhibits cyclooxygenase-2 (COX-2) over cyclooxygenase-1 (COX-1). By selectively blocking COX-2, it reduces the synthesis of pro-inflammatory prostaglandins (e.g., PGE2) at sites of inflammation, thereby providing analgesic, anti-inflammatory, and antipyretic effects. Its selectivity for COX-2 minimizes inhibition of COX-1-derived prostaglandins that are important for gastrointestinal mucosal protection, platelet function, and renal perfusion, thus reducing the risk of certain adverse effects compared to non-selective NSAIDs.

Pharmacodynamics: Firocoxib exhibits potent anti-inflammatory, analgesic, and antipyretic activity. In animal models, it has been shown to reduce inflammation and pain associated with osteoarthritis and postoperative pain. Its COX-2 selectivity is high (e.g., >380-fold in dogs), which contributes to a favorable gastrointestinal safety profile. The drug does not significantly affect platelet aggregation at therapeutic doses. Clinical effects are typically observed within hours of administration and peak around 24 hours.

⚡ Pharmacokinetics Summary

Absorption: Firocoxib is well absorbed after oral administration in dogs and horses. In dogs, oral bioavailability is approximately 80%. Peak plasma concentrations occur within 1-2 hours after dosing. In horses, absorption is slower, with peak concentrations at about 2-4 hours.
Distribution: Firocoxib is highly protein-bound (>90%) in plasma. It distributes widely into tissues, with concentrations in synovial fluid reaching approximately 50-60% of plasma concentrations. The volume of distribution is moderate, indicating distribution into extracellular fluid.
Metabolism: Firocoxib is extensively metabolized in the liver, primarily via oxidation and glucuronidation. The major metabolic pathways involve cytochrome P450 enzymes (CYP) and UDP-glucuronosyltransferases. In dogs, multiple metabolites are formed, but the parent drug is the predominant circulating entity.
Excretion: Firocoxib is eliminated primarily via biliary excretion into feces, with a smaller amount excreted in urine. In dogs, approximately 70% of the dose is recovered in feces and 20% in urine. The elimination half-life is approximately 7-8 hours in dogs and 30-40 hours in horses.
Half-Life: Dog: ~7-8 hours; Horse: ~30-40 hours
Bioavailability: Oral: ~80% in dogs; ~70-80% in horses
Protein Binding: >90% in dogs and horses

Available Formulations & Strengths

Oral Tablet 57 mg, 68 mg, 136 mg, 227 mg (Oral)
Oral Paste 0.82% (w/w) paste (equivalent to 7.5 mg/g) (Oral)

Contraindications & Clinical Warnings

Contraindications:
  • Known hypersensitivity to firocoxib or other NSAIDs
  • Concurrent use with other NSAIDs or corticosteroids
  • Pre-existing gastrointestinal ulceration, bleeding, or perforation
  • Renal or hepatic impairment
  • Dehydration, hypovolemia, or hypotension
  • Breeding, pregnant, or lactating animals (safety not established)
  • Animals younger than 6 months of age (dogs) or 12 months of age (horses)
Warnings & Clinical Precautions:
  • Use with caution in animals with a history of GI intolerance to NSAIDs.
  • Monitor renal function in animals with pre-existing renal disease or those receiving concurrent diuretics or ACE inhibitors.
  • Use the lowest effective dose for the shortest duration necessary.
  • Do not use in animals with bleeding disorders or those undergoing surgery where hemostasis is critical.
  • In horses, avoid use in neonates or foals; safety in breeding stallions and mares has not been established.
  • In dogs, safety has not been established for use beyond 30 days; periodic monitoring of liver and kidney function is recommended for long-term therapy.
  • Administer with food to reduce GI adverse effects.
  • Do not use in cats due to lack of safety data and potential for toxicity.

Adverse Effects & Reactions

Common:

  • Vomiting
  • Diarrhea
  • Decreased appetite
  • Lethargy
  • Increased thirst or urination

Serious / Severe:

  • Gastrointestinal ulceration or perforation
  • Renal toxicity (acute renal failure)
  • Hepatic toxicity (elevated liver enzymes, jaundice)
  • Blood dyscrasias (rare)

Rare:

  • Idiosyncratic reactions
  • Allergic reactions (skin rash, anaphylaxis)
  • Neurological signs (ataxia, seizures)

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Other NSAIDs (e.g., carprofen, meloxicam) Additive risk of GI ulceration, renal toxicity, and bleeding. High
Corticosteroids (e.g., prednisone, dexamethasone) Increased risk of GI ulceration and perforation. High
Diuretics (e.g., furosemide) Increased risk of renal toxicity due to reduced renal perfusion. Moderate
ACE inhibitors (e.g., enalapril) or angiotensin receptor blockers Additive effects on renal function; may increase risk of renal impairment. Moderate
Anticoagulants (e.g., warfarin, heparin) Increased risk of bleeding due to platelet inhibition (though firocoxib has minimal effect on platelets, caution is advised). Moderate
Fluoroquinolone antibiotics (e.g., enrofloxacin) Possible increased risk of seizures in some animals. Mild

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea (possibly bloody)
  • Lethargy
  • Loss of appetite
  • Abdominal pain
  • Increased thirst and urination
  • In severe cases: seizures, coma, renal failure, GI perforation

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce emesis if ingestion is recent (within 2 hours) and the animal is conscious. Administer activated charcoal to reduce absorption. Provide intravenous fluids to maintain renal perfusion and correct dehydration. Monitor renal and hepatic function. Use gastroprotective agents (e.g., misoprostol, sucralfate, H2 antagonists or proton pump inhibitors) to prevent or treat GI ulceration. In severe cases, consider hemodialysis or peritoneal dialysis. There is no specific antidote for firocoxib overdose.

Food Animal Withdrawal Times

Firocoxib is not approved for use in food-producing animals. Therefore, no withdrawal times have been established. Use in food animals is prohibited.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20°C to 25°C (68°F to 77°F), with excursions permitted between 15°C and 30°C (59°F and 86°F).

Handling & Special Conditions: Protect from moisture. Keep container tightly closed. Do not remove desiccant from the bottle.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved by the FDA for use in dogs (Previcox) and horses (Equioxx).

Extra-Label (Off-Label) Use: In the United States, firocoxib is approved for use in dogs and horses. Extra-label use in other species is permitted under the Animal Medicinal Drug Use Clarification Act (AMDUCA) only with a valid veterinarian-client-patient relationship and appropriate withdrawal times, but due to lack of data, extra-label use is discouraged. In food animals, extra-label use is prohibited.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Firocoxib is a highly selective COX-2 inhibitor that provides effective pain relief and anti-inflammatory action with a favorable safety profile compared to non-selective NSAIDs. It is commonly used in dogs for osteoarthritis and postoperative pain, and in horses for similar indications. Dosing is once daily, which improves owner compliance. In dogs, the approved dose is 5 mg/kg orally once daily, and in horses, 0.1 mg/kg orally once daily. It is important to administer with food to minimize GI upset. Contraindications include concurrent use with other NSAIDs or corticosteroids, and use in animals with GI ulceration, renal or hepatic disease, or dehydration. Monitoring for adverse effects, especially GI and renal, is recommended, particularly during long-term therapy. In horses, the duration of therapy should not exceed 14 days. Firocoxib is not approved for cats, and its use in cats is not recommended due to lack of safety data. For food animals, it is not approved and should not be used. Always follow label instructions and consult a veterinarian for appropriate use.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)