Binding of chlorpromazine, phenytoin and aspirin to the erythrocytes and lipoproteins in whole human blood

The quantitative binding of 14C-labelled chlorpromazine, phenytoin or aspirin (at 10 microM) to blood cells and plasma lipoproteins in whole human blood or to the washed erythrocytes in an isotonic protein-free medium has been studied. The fractions of chlorpromazine, phenytoin and aspirin bound to the blood cells in whole blood amounted to about 40, 14 and 2% of the total amount added, and those to the lipoproteins amounted to 7, 2 and 1%, respectively. Their binding to the washed erythrocytes in protein-free medium was 95, 76 and 40%, respectively. Their octanol:water partition coefficients were 214, 170 and less than 0.1, respectively. These results suggest that the amphiphilic drugs with relatively high hydrophobicity may be bound to the blood cells, mainly to erythrocytes, to considerable extents when administered clinically, and also that their binding to plasma lipoproteins may not be negligible.