Objective: Recent findings suggest that permanent blockade of cyclooxygenase 2 (COX-2) is one factor contributing to the cardiovascular side effects of selective COX-2 inhibitors (coxibs) and nonsteroidal antiinflammatory drugs (NSAIDs). The present study compared the extent and time course of COX-2 inhibition and the effects on cardiovascular parameters (changes in blood pressure and heart rate) between various antirheumatic doses of diclofenac, celecoxib, and rofecoxib in healthy elderly volunteers.
Methods: A randomized, parallel-group study was conducted in volunteers receiving 75 mg diclofenac twice daily, 200 mg celecoxib twice daily, or 25 mg rofecoxib once daily for 8 days. Blood samples were obtained predose and at specified time points postdose, on days 1 and 8, for assay of drug plasma concentrations and COX-2 inhibition. Lipopolysaccharide-induced prostaglandin E(2) synthesis was measured ex vivo as an index of COX-2 activity in human whole blood.
Results: COX-2 inhibition was significantly less pronounced after treatment with celecoxib and rofecoxib than with diclofenac. Maximal inhibitions after a single dose and at steady state, respectively, were as follows: 99% and 99% with diclofenac, 70% and 81% with celecoxib, and 56% and 72% with rofecoxib. At steady state, only diclofenac caused virtually complete COX-2 inhibition over the whole dose interval, and this corresponded to the highest increase in systolic blood pressure and greatest reduction in heart rate.
Conclusion: Diclofenac elicited the most pronounced COX-2 inhibition, blood pressure elevation, and suppression of heart rate. It is assumed that the extent and time course of intravascular COX-2 inhibition may determine the differential profile of cardiovascular side effects associated with NSAIDs and coxibs, but this has to be proven in future studies.