Binding of busulfan to plasma proteins and blood cells

The reversible and non-reversible binding of busulfan to plasma proteins and to blood cells has been evaluated in man. The reversible binding to plasma proteins was insignificant in both healthy subjects and in patients with chronic myelocytic leukaemia. The percentage of busulfan irreversibly bound to plasma ligands was 32.4. Busulfan was distributed evenly between blood cells and plasma. The fraction of busulfan irreversibly bound to the blood cells was 46.9%. The major portion of busulfan that is degraded in whole blood reacts with the blood cells and the main part of that binds to macromolecular components in the cells.