More pronounced inhibition of cyclooxygenase 2, increase in blood pressure, and reduction of heart rate by treatment with diclofenac compared with celecoxib and rofecoxib

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 anti-inflammatory 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 I and 8, for assay of drug plasma concentrations and COX-2 inhibition. Lipopolysaccharide-induced prostaglandin E, 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.