Complex Formation of Cyclodextrins with Sulfasalazine in Buffer Solutions

Complex formation of alpha-, beta-, and gamma-cyclodextrins with sulfasalazine in biologically relevant buffer solutions (pH 1.2 and 7.4) was studied. Formation of inclusion complexes of 1 : 1 stoichiometry between the drug and cyclodextrins was revealed. The ionization state of sulfasalazine more strongly affects the complex formation than does the structure of cyclodextrins. Compared with a neutral molecule, sulfasalazine anionic species forms with cyclodextrins more stable complexes, which are essentially stabilized by possible surface interactions.