Binding of sulfisoxazole to protein fractions of tears

By using equilibrium dialysis experiments, it is shown that sulfisoxazole binds extensively with albumin and alpha-globulin and to a lesser extent with gamma-globulin and lysozyme, all of which are normal components of tears. The binding of sulfisoxazole to the various protein fractions quantitatively accounts for the over-all binding of this drug to human tears. It is suggested that to predict the binding of drugs to proteins in lacrimal fluid, both in normal and pathological conditions, it is necessary to conduct binding studies of the drug with the major protein fractions of tears. More-over, it is essential to know the composition of the major protein fractions of tears in both normal and various pathological conditions to conduct the necessary in vitro binding studies.