This process, called enterohepatic recirculation,
allows naproxen to remain in the body for an extended period of time.
A second COX - 2 inhibitor, Pfizer Inc.'s Celebrex, was
allowed to remain on the market with the condition that Pfizer conduct a study to prove that Celebrex was no worse than two older NSAIDs,
naproxen and ibuprofen.