Concentrations of ibuprofen and the protein and pH value of synovial fluid and plasma following oral administration of ibuprofen in patients with 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 μg/ml, the concentration in the synovial fluid was 9.4 μg/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