Kinetics of salicylates in blood and joint fluid.

Samples of blood and joint fluid from 30 patients who had taken acetylsalicylic acid were examined for concentrations of total salicylates. The data were arranged in groups according to diagnosis of the joint disease. Analysis of the data did not show significant differences in the kinetics of total salicylates into blood. In groups, the time to first appearance of 0.3 mg/liter averaged 6 minutes, and levels "close to maximum" concentration averaged about 23.0 mg/liter. Time to first appearance of 0.3 mg/liter of total salicylates in joint lfuid ranged from 10 to 31 minutes. The average level of maximum concentration of total salicylates in joint fluid was 14.8 mg/liter. Transport of total salicylates from blood to joint fluid showed a pattern consistent with the type of joint disease. Support was found for the hypothesis that diffusion was the major factor in the process of movement of total salicylates from blood to joint fluid. The histopathologic changes in different types of synovitis influenced the biophysical properties of the inner part of the joint capsule.