Firocoxib (ML 1785713) is a potent, selective and orally active COX-2 inhibitor with an IC₅₀ of 0.13 μM. Firocoxib shows 58-fold more selective for COX-2 than COX-1 (IC₅₀ of 7.5 μM). Firocoxib has anti-inflammatory effects^[1]. In Vitro: The COX-1:COX-2 selectivity ratios generally are established by comparing the IC₅₀ for COX-1 to the IC₅₀ for COX-2. The IC₈₀ value more closely resembles the steady-state plasma drug concentration than does the IC₅₀ value^[1].
The selectivity ratio for Firocoxib based on the IC₈₀ values is 121 (IC₈₀ of 0.36 μM and 43.6 μM for COX-2 and COX-1, respectively), indicating that selectivity for COX-2 is not reduced at concentrations higher than the IC₅₀. Notably, Firocoxib concentrations that yield 80% to 95% inhibition of COX-2 produce < 20% inhibition of COX-1^[1]. In Vivo: Firocoxib (0.75-1.5mg/kg; oral gavage; female domestic shorthair cats) treatment efficacious in attenuating fever when administered to cats 1 or 14 hours before LPS challenge^[1].
Pharmacokinetic properties of Firocoxib are determined after i.v. (2 mg/kg) and oral (3 mg/kg) administration in male cats. Firocoxib has moderate to high oral bioavailability (54% to 70%), low plasma clearance (4.7 to 5.8 mL/min/kg), and an elimination half-life of 8.7 to 12.2 hours^[1].