The pharmacokinetics of flurbiprofen in younger and elderly patients with rheumatoid arthritis.

The pharmacokinetics of flurbiprofen (Ansaid Tablets, Upjohn Company of Canada, Don Mills, Ontario) were evaluated in both younger (40 to 60 years) and elderly (65 to 83 years) rheumatoid arthritic patients after both a 100-mg single-dose administration and at steady state during a 100-mg twice-a-day dosage regimen. Both flurbiprofen plasma concentration-time profiles and the urinary excretion of flurbiprofen and its major metabolites were evaluated. The results indicate that the pharmacokinetics of flurbiprofen are linear in both age groups based on only minor changes between single-dose and steady-state parameter determinations and the agreement between calculated and predicted accumulation values in plasma concentrations. Only minor differences in the pharmacokinetic parameters were observed between the younger and elderly patients. Only free flurbiprofen clearance was found to have a significant but variable correlation to patient age. The effect of flurbiprofen on the urinary excretion of two prostaglandins were also evaluated throughout this study. In both age groups, the maximum decrease in urinary excretion was observed after the first dose, and this effect was maintained throughout the remainder of the study. Percent decreases from baseline in urinary excretion during drug administration were similar for both age groups. Similar side-effect profiles were observed between age groups.