This enzyme occurs at high levels at sites of inflammation, where it is induced by mediators of inflammation. However, inhibition of COX-1 is undesirable, since it plays an important role in various physiological processes such as platelet aggregation, and maintenance of the GI mucosal barrier. Peak plasma concentrations of celecoxib occur about three hours following an oral dose. The drug is highly protein-bound, primarily to albumin. It is metabolized mainly by cytochrome P450 2C9 to inactive metabolites.
Elimination occurs predominantly by hepatic metabolism.
The terminal half-life is somewhat variable, but is approximately 11 hours. The usual dosage of celecoxib for OA is 200 mg once daily or 100 mg twice daily. In RA, the recommended starting dosage is 100 mg twice daily, increasing to 200 mg twice daily, if needed. Celecoxib may be given with or without food. Dosage adjustment is not usually required in the elderly, but the lowest starting dosage should be used in elderly patients who weigh less than 50 kg.