Celecoxib is one of the few Non-Steroidal Anti-Inflammatory Drug (aka FANS) which is designed for reactiong ONLY with COX2 enzyme, which is specific of the inflammatory process, and not a constitutive enzyme as COX1.
If you know the difference in between COX1 and 2, you know that they have different active sites. The SO2 group is of paramount importance because it binds with an arginine and this is a key factor for the stability of the molecule in the active site.
Because of its properties, celebrex (celecoxib capsules) is a gastro-resistant capsule as pharmaceutical form and is soluble in digestive fluids.