Vioxx is more selective, and Arcoxia is the most selective of all, blocking out Cox-2 while not affecting Cox-1.    From Wordnik.com.  [Vioxx, The Sequel] Reference

Cox-1 and cox-2 are different forms of cyclooxygenase, an enzyme whose activity increases inflammation and pain.    From Wordnik.com.  [Medlogs - Recent stories] Reference