Celecoxib

Unlike most NSAIDs, which inhibit both types of cyclooxygenases (COX-1 and COX-2), celecoxib is a selective noncompetitive inhibitor of cyclooxygenase-2 (COX-2) enzyme. COX-2 is expressed heavily in inflamed tissues where it is induced by inflammatory mediators. The inhibition of this enzyme reduces the synthesis of metabolites that include prostaglandin E2 (PGE2), prostacyclin (PGI2), thromboxane (TXA2), prostaglandin D2 (PGD2), and prostaglandin F2 (PGF2). Resultant inhibition of these mediators leads to the alleviation of pain and inflammation.

By inhibiting prostaglandin synthesis, non-steroidal anti-inflammatory drugs (NSAIDs) cause mucosal damage, ulceration and ulcer complication throughout the gastrointestinal tract. Celecoxib poses less of an ulceration risk than other NSAIDS, owing to its decreased effect on gastric mucosal prostaglandin synthesis when compared to placebo.

Celecoxib exerts anticancer effects by binding to the cadherin-11 (CDH11)protein, which is thought to be involved in the progression of tumors, and inhibiting the 3-phosphoinositide-dependent kinase-1 (PDK-1) signaling mechanism. In addition, celecoxib has been found to inhibit carbonic anhydrase enzymes 2 and 3, further enhancing its anticancer effects.

As mentioned in the pharmacodynamics section of this drug entry, celecoxib may cause an increased risk of thrombotic events. The risk of thrombosis resulting from COX-2 inhibition is caused by the vasoconstricting actions of thromboxane A2, leading to enhanced platelet aggregation, which is uncontrolled when the actions of prostacyclin, a platelet aggregation inhibitor, are suppressed through the inhibition of COX-2.