Firocoxib is a COX-2 inhibitor commonly used in veterinary medicine. This article provides a comprehensive overview of firocoxib's pharmacology, mechanisms of action, interactions and potential uses.
Firocoxib is an effective COX-2 inhibitor for controlling pain and inflammation in canines and equines. With appropriate patient screening and dose adjustment based on individual risk factors, it provides clinicians an important therapeutic option for osteoarthritic and post-operative patients.
Mechanism of Action:
Firocoxib selectively inhibits COX-2 over COX-1. This allows it to provide anti-inflammatory and analgesic effects while sparing the protective prostaglandins produced via COX-1. By blocking COX-2, it prevents the conversion of arachidonic acid to prostaglandin H2 and subsequently other prostanoids like PGE2 and PGF2α which mediate pain and inflammation.
Approved Uses:
In dogs, studies have shown firocoxib API reduces lameness associated with osteoarthritis when given orally once daily at a dose of 0.27-0.45 mg/kg. In horses, it is approved for control of pain and inflammation associated with musculoskeletal disorders at an oral dose of 0.1-0.25 mg/kg once daily.
Pharmacokinetics:
Food does not significantly affect absorption in dogs but may prolong Tmax in horses. It is extensively metabolized in the liver by CYP2C9 to form a phenolic glucuronide conjugate which is inactive and undergoes biliary/urinary excretion.
Drug Interactions:
CYP2C9 inhibitors like fluconazole may increase firocoxib levels while CYP2C9 inducers like rifampin may decrease them. Care should be taken with concomitant use of other non-steroidal anti-inflammatories or corticosteroids due to additive effects.
Adverse Effects:
Renal toxicities are usually reversible if detected early and drug discontinued. GI effects like vomiting can be reduced by giving with food, although this affects PK in horses. Platelet function tests may be indicated in high-risk patients to monitor for effects on coagulation.
