The following is the structure of Celebrex.

 The following is another sketch of the molecule with all of the functional groups identified. 

Chemical Aspects of Celebrex:
 There are three acid/base functional groups on Celebrex.  They are (1) the sulfonamide, (2) the tertiary amine, (3) the secondary amine.  Below are the dissociation products for each acid/base group.
Dissociation of Secondary amine:

Dissociation of Tertiary amine:

Dissociation of Sulfonamide:

       Celebrex will be largely dissolved in the stomach.  The pka of the secondary amine is approximately 6.  Therefore, in the acidic pH of the stomach (between 1 and 3), the Celebrex will be protonated as shown above.  This protonated molecule will be positively charged.  This positive charge means that the drug will be easily hydrated in an aqueous solution, and therefore will be dissolved.  Celebrex will only be able to absorb in the lower small intestine.  As the molecule moves through the small intestines the pH will get closer to the pka.  As this happens more of the molecule will dissociate and become unprotonated.  This dissociation will leave the Celebrex as an uncharged hydrophobic molecule.  These two properties favor absorption through the small intestine.   It has been documented that Celebrex does cross the blood-brain barrier.  Celebrex is a hydrophobic molecule and, therefore, is able to cross the blood-brain barrier.