Disopyramide, enantiomer protein binding

For enantiomeric drugs with low organ clearance, differences in renal or hepatic clearance between stereoisomers may reflect their free fraction in the plasma and not real stereoselectivity of the ability of the organ to remove the free enantiomers (intrinsic clearance) from the plasma. Clearance differences between stereoisomers of verapamil and disopyramide may be a function of plasma protein binding differences. In addition, volumes of distribution as well as concentration ratios of stereoisomers in body fluids to total plasma and blood are influenced by plasma protein binding. For example, the larger volume of distribution and greater total body clearance of R-disopyramide compared to the S isomer may be explained by the lower... 

H. Takahashi, H. Ogata, and Y. Seki, Binding interaction between enantiomers of disopyramide and mono-N-dealkyldisopyramide on plasma protein, Drug Melab. Dispos., 19 554 (1991). 

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