[Concentrations of ibuprofen and the protein and pH value of synovial fluid and plasma following oral administration of ibuprofen in patients with arthritis].

Concentrations of Ibuprofen and Protein Concentration and pH-Value in Synovial Fluid and Plasma Following Oral Administration of Ibuprofen in Patients Suffering from Arthritis. In 16 patients suffering from arthritis of the knee the concentration of ibuprofen in the synovial fluid was examined in correlation with the synovial fluid volume, cell count, pH value and protein concentration. The mean ibuprofen concentration in plasma 4 h after oral administration of 400 mg ibuprofen amounted to 15.45 micrograms/ml, the concentration in the synovial fluid was 9.4 micrograms/ml. Due to the inflammatory nature of the effusions the protein concentration in the synovial fluid was evidently increased to an average of 4.46 g/dl and thus was about 65% of the mean plasma protein concentration of 6.88 g/dl. The ibuprofen in the synovial fluid showed a correlation to the protein concentration. On the other hand, there were no significant differences between the pH value in the plasma and in the synovial fluid. There was no tendency to an acid pH. Furthermore, there was no correlation between ibuprofen concentration and cell count. The tests showed that the "accumulation" of the nonsteroidal antiinflammatory drug in the synovial fluid is positively correlated with the high protein concentration but not with the pH value.