Firocoxib

Overview

Firocoxib (Previcox®) is a nonsteroidal anti-inflammatory drug (NSAID) used in dogs for the control of pain and inflammation, particularly in orthopedic and chronic musculoskeletal conditions such as osteoarthritis.

It is a selective cyclooxygenase-2 (COX-2) inhibitor, which helps reduce inflammation and pain while minimizing effects on COX-1–mediated physiological functions. In addition to its anti-inflammatory action, it provides analgesic and antipyretic effects.

Firocoxib is commonly administered once daily and may be used for both chronic conditions and perioperative pain management. When used for surgical pain, give the first dose about 2 hours before the procedure.

Mechanism of Action (MOA): Firocoxib selectively inhibits the COX-2 enzyme, reducing the production of prostaglandins involved in inflammation, pain, and fever, while sparing COX-1–mediated protective functions such as gastrointestinal and renal homeostasis.

Indications

Firocoxib is used in dogs for the management of pain and inflammation associated with both chronic and acute conditions, particularly those involving the musculoskeletal system.

• Osteoarthritis: Relief of pain and inflammation associated with degenerative joint disease.
• Postoperative pain management: Used for soft tissue, orthopaedic and dental surgery in dogs; when used for perioperative pain, give the first dose about 2 hours before surgery.
• Adjunct in neoplastic conditions: May have an adjunctive role in transitional cell carcinoma of the urinary bladder: it has antitumour effects of its own and acts synergistically with platinum-based chemotherapy such as cisplatin.
• Inflammatory colorectal polyps: An extra-label use reported in a case series of miniature dachshunds, in which firocoxib was given alongside chlorambucil.

Dosage (Reference)

Dog

In dogs, firocoxib is administered once daily for the management of pain and inflammation associated with osteoarthritis or surgical procedures.

Cat

Routine use in cats is not recommended. A single oral dose of about 1.5 mg/kg has been studied for short-term febrile and postoperative pain, but long-term safety in cats has not been determined.

Warnings & Precautions

Firocoxib, like other NSAIDs, requires careful patient selection and monitoring due to potential gastrointestinal, renal, and systemic effects, particularly in compromised patients.

• Perioperative use: Administer cautiously around anesthesia, as NSAIDs may reduce renal perfusion during hypotension. If hypotension is anticipated, delay administration until the patient is stable and normotensive.
• Hydration and perfusion status: Do not use in dehydrated, hypovolemic, or hypotensive patients due to increased risk of renal injury.
• Gastrointestinal disease: Avoid use in patients with existing GI ulceration or irritation.
• Coagulation disorders: Use is contraindicated in patients with bleeding disorders.
• Renal disease: Use cautiously and assess risk before administration due to potential impact on renal function.
• Age and body weight limitations: Do not use in dogs younger than 10 weeks of age or weighing under 3 kg. The US label instead warns that doses above 5 mg/kg in puppies younger than 7 months have caused serious adverse reactions, including death, and states that dogs under 12.5 lb (5.7 kg) cannot be accurately dosed.
• Pregnancy and lactation: Contraindicated in pregnant or lactating animals.
• Hypersensitivity: Do not use in patients with known hypersensitivity to firocoxib or to other NSAIDs.
• Hepatic, cardiovascular disease and diuretic therapy: Use cautiously and with enhanced monitoring in patients with pre-existing hepatic or cardiovascular dysfunction, and in patients receiving diuretic therapy.
• Geriatric patients: Monitor geriatric patients closely throughout treatment: many have reduced renal function, and firocoxib is often used to treat osteoarthritis in these patients.
• Juvenile dogs: In puppies 10–13 weeks old treated for six months, 5 mg/kg produced subclinical periportal hepatic fatty changes in half the animals; 15–25 mg/kg increased these changes and was associated with death or euthanasia.
• Breeding animals: Safety in breeding dogs has not been established; no adverse effects have been reported in breeding animals, but data are lacking.
• Cardiac failure (human data): NSAIDs carry a small risk of precipitating cardiac failure in humans; whether this risk occurs in animals is unknown.

Drug Interactions

Interactions with firocoxib are primarily related to additive gastrointestinal, renal, and systemic toxicity when combined with other drugs affecting similar pathways.

• Other NSAIDs: Do not administer concurrently with another NSAID or within 24 hours of one; combining NSAIDs may increase the risk of gastrointestinal toxicity.
• Glucocorticoids: Concurrent use increases the risk of severe gastrointestinal adverse effects, including ulceration and bleeding.
• Nephrotoxic drugs (e.g., aminoglycosides): Increased risk of renal injury when used together.
• Washout periods: Allow a 3–5 day washout after stopping firocoxib before starting another NSAID. The optimal interval between an NSAID and a glucocorticoid is unknown, but 3–5 days between the two classes is likewise recommended.
• ACE inhibitors and diuretics: NSAIDs may reduce the effects of ACE inhibitors and diuretics; use firocoxib cautiously, with enhanced monitoring, in dehydrated, hypovolaemic or hypotensive patients and in those receiving diuretics.
• Protein-bound drugs / methotrexate: Because firocoxib is more than 95% protein bound, it could theoretically displace other highly protein-bound drugs, although this has not been shown to be clinically important. Use with methotrexate only with extreme caution, as serious toxicity has occurred when NSAIDs were given concurrently.
• Digoxin and fluconazole: Digoxin: NSAIDs may increase serum digoxin concentrations. Fluconazole: has increased celecoxib levels in humans and could potentially increase firocoxib levels in dogs.

Side Effects & Overdose

Side Effects

Adverse effects of firocoxib are similar to other NSAIDs and are primarily related to gastrointestinal irritation, with variability between individual patients.

• Gastrointestinal signs: Vomiting, diarrhoea or decreased appetite may occur; in pre-approval studies vomiting and anorexia were reported in approximately 4% and 2% of dogs respectively. Stop therapy if signs persist beyond 1–2 days.
• Gastrointestinal ulceration or bleeding: Suspected cases require immediate discontinuation.
• Individual variability: Some animals may tolerate one NSAID but not another.
• Postapproval adverse reports: Postapproval reports have included azotaemia, proteinuria, urinary incontinence, kidney failure, increased ALP, ALT and bilirubin, lethargy or depression, anaemia, tachycardia, pruritus and dermatitis; these are voluntary reports and do not establish incidence or causation.

Overdose

Overdose or repeated dosing in susceptible patients may increase the risk of toxicity, particularly in those with impaired drug metabolism.

• Exaggerated adverse effects: Doses five times the recommended dose have caused gastrointestinal problems in dogs.
• Drug accumulation: May occur in patients with hepatic disease due to reduced metabolism.
• Management: Discontinue therapy. After a known or suspected overdose, consider gastric decontamination and supportive treatment such as IV fluids and oral sucralfate, monitor gastrointestinal and renal status, and consult a 24-hour veterinary poison-control service.
• Acute toxicity data: Acute-overdose data in animals are limited; the reported oral LD50 in rats is greater than 2 g/kg.

Key Notes

Practical clinical insights to optimize the use of firocoxib in dogs:

• COX-2 selectivity: In canine whole-blood assays firocoxib is approximately 384-fold more selective for COX-2; this in-vitro selectivity does not necessarily predict superior clinical efficacy or safety.
• Once-daily dosing: Firocoxib is administered once daily.
• Flexible administration: May be given with or without food; feeding delays absorption but does not reduce the overall amount absorbed.
• Perioperative use: May be used as part of a perioperative pain plan, with the first dose given about 2 hours before surgery.
• Potential anticancer role: May provide additional benefit in certain neoplastic conditions, particularly urinary bladder tumors.
• Pharmacokinetics: In dogs, oral bioavailability is about 38%, protein binding about 96%, and the elimination half-life about 6–8 hours. Firocoxib is metabolised in the liver and eliminated principally in bile and faeces. Food does not reduce total absorption, but delays peak concentrations from about 1 hour in fasted dogs to about 5 hours in fed dogs.
• Monitoring: Monitor clinical efficacy and adverse effects, with baseline and periodic physical examination, CBC, serum chemistry including electrolytes, and urinalysis; periodically assess water intake, BUN, creatinine and urine specific gravity.
• Storage: Store the chewable tablets in a tightly sealed container, protected from light, at room temperature (15–30°C / 59–86°F); brief excursions up to 40°C (104°F) are permitted. The stability of compounded formulations has not been evaluated.
• Client advice: Give with or without food, although food may reduce the chance of stomach upset; if the dog vomits on an empty stomach, try giving it with food. Tell owners to stop the drug and contact the practice if they see reduced appetite, persistent vomiting or diarrhoea, a change in behaviour or activity, a change in drinking or urination, or yellowing of the gums, skin or whites of the eyes.