Drug-cyclodextrin association constants determined by surface tension and surface pressure measurements - I. Host-guest complexation of water solubledrugs by cyclodextrins: Polymyxin B-beta cyclodextrin system

The complexation reaction between the amphiphilic peptide antibiotic polymy xin B and naturally occurring cyclodextrins, used as potential drug carrier s, was quantitatively evaluated from surface tension measurements at variou s drug concentrations, The association constant, K-a, of polymyxin B:beta-c yclodextrin inclusion complex formation of 1:1 stoichiometry was determined from the change in the drug interfacial activity upon the addition of beta -cyclodextrin at the excess solution concentration (10(-3) M). The obtained K-a value is discussed in terms of molecular matching of the host cyclodex trin cavity and the guest drug molecule. (C) 1999 Academic Press.