The distribution of proquazone and three of its metabolites in serum and synovial fluid.

In 13 patients with hydrarthrosis of the knee, samples of synovial fluid and blood were drawn at regular intervals, following a single oral dose of 600 mg proquazone. The concentrations of the unchanged drug were measured fluorimetrically and those of its three principal, active metabolites by high pressure liquid chromatography. The absorption and distribution of proquazone and its metabolites were rapid. Measurable--in some cases considerable--concentrations were to be found in both the synovial fluid and serum as early as 30 minutes after intake. High concentrations were still present up to 7 hours after intake. Considerable variations were observed, both between patients and over time for each patient, so that only qualitative rather than quantitative kinetic conclusions could be drawn from the results. The concentrations were generally lower in the synovial fluid than in the serum, which may be ascribed to the drug's high protein binding.