Research suggested most of the adverse effects of NSAIDs to be mediated by blocking the COX1 (constitutive) enzyme, with the analgesic effects being mediated by the COX2 (inducible) enzyme. Thus, the COX2 inhibitors were developed to inhibit only the COX2 enzyme (traditional NSAIDs block both versions in general).
Research indicated that most of the adverse effects of NSAIDs are mediated by blocking the COX1 (constitutive) enzyme, while analgesic effects are mediated by the COX2 (inducible) enzyme. Consequently, COX2 inhibitors were developed to specifically inhibit only the COX2 enzyme (traditional NSAIDs generally block both versions).