D-penicillamine and D-penicillamine-protein disulphide in plasma and synovial fluid of patients with rheumatoid arthritis.

1. The plasma pharmacokinetics of D-penicillamine (D-pen) and D-penicillamine-albumin disulphide (D-pen-alb) were examined over a dosage interval in six patients with rheumatoid arthritis. In two of these, 24 h synovial fluid profiles of D-pen and D-pen-alb were also obtained. 2. D-pen was undetectable in plasma at the beginning of the study. The peak concentration (5.4 +/- 1.2 microM) occurred at between 45 min and 2 h and the mean elimination half-life was 0.6 h. D-pen-alb, however, was present at a mean plasma concentration of 19.1 microM prior to dosage, peaked at 26.2 microM and was eliminated with a half-life of 40 h. 3. D-pen concentrations in synovial fluid rose more slowly and peaked lower than in plasma. D-pen-alb was present in synovial fluid of the patients at 50.1% and 83.6%, respectively, of the simultaneous plasma concentration prior to dosage. Concentrations varied during the study interval, corresponding to changes in plasma concentrations. 4. These results demonstrate that D-pen forms stable conjugates with protein in treated patients. The presence of D-pen-alb in relatively high concentrations throughout the dosage interval contrasts with the low concentrations and rapid elimination of D-pen. Both D-pen and D-pen-alb were also shown to be present at the putative site of drug action (the inflamed synovial joint) in concentrations lower than those in plasma.