Diclofenac binding to albumin and lipoproteins in human serum.

The binding of diclofenac to human serum albumin (HSA) and to lipoproteins was studied in vitro by equilibrium dialysis. Binding to HSA is characterized by two classes of sites with one site each (K1 = 5 X 10(5) M-1 and K2 = 0.6 X 10(5) M-1). The binding to lipoproteins was shown to be saturable with a larger number of binding sites and low association constants. The evidence of two specific binding sites on HSA was confirmed by circular dichroism data. In addition, an identification of those sites was performed by displacement of fluorescent probes. The data show that the high affinity site (K1 = 5 X 10(5) M-1) is likely to be shared by benzodiazepines while the second one (K2 = 0.6 X 10(5) M-1) is common with the warfarin site.