SOME FLUORESCENT INVESTIGATIONS OF THE INTERACTION BETWEEN THE ENANTIOMERS OF WARFARIN AND HUMAN-SERUM ALBUMIN

The fluorescence of warfarin is greatly enhanced on binding to a single site on human serum albumin. Other sites make only very small contributions to this enhancement. Advantage is taken of this phenomenon to estimate a binding constant for the binding of R, S and racemic warfarins to human serum albumin. Many measurements are made at the clinically significant low drug-to-protein ratios. The binding constant for the S-isomer is higher than that of the R. The abilities of phenylbutazone, ibuprofen, fenoprofen, tolmetin and aspirin to displace warfarin from this site on albumin is investigated at very slow drug-to-protein ratios. Investigations of the binding of warfarin as a function of pH suggest that the affinity is different for the N and B forms of albumin. The binding to both the N and B forms is affected by chloride ions. © 1979.