Interactions of amphiphilic drugs with α-, β-, and γ-cyclodextrins

• Published in: Colloid and polymer science 1993-05, Vol.271 (5), p.499-506
• Main Authors: TAKISAWA, N, SHIRAHAMA, K, TANAKA, I
• Format: Article
• Language: English
• Subjects: Applied sciences; Biological and medical sciences; Exact sciences and technology; General pharmacology; Medical sciences; Natural polymers; Pharmaceutical technology. Pharmaceutical industry; Pharmacology. Drug treatments; Physicochemistry of polymers; Starch and polysaccharides
• ISSN: 0303-402X; 1435-1536
• DOI: 10.1007/BF00657395

The association of several amphiphilic drugs with alpha -, beta -, and gamma -cyclodextrins has been measured by use of drug-sensitive electrodes. Drugs investigated are hydrochlorides of chlorpromazine, dibucaine, tetracaine, and procaine, and valethamate bromide. Each drug forms the drug:cyclodextrin = 1:1 complex with alpha - and beta -cyclodextrin, and both the 1:1 and 2:1 complex with gamma -cyclodextrin, except valethamate which only forms the 1:1 complex. The strength of the 1:1 complex formations is in the order of beta -CyD> alpha -CyD> gamma -CyD. The association constant of the 2:1 complex in drug- gamma -CyD is larger than that of 1:1 complex. The free energy change of the complex formation has a positive correlation with that of the micelle formation of drugs. The deviation from this relation is explained in terms of fittability of the bulky hydrophobic group of drugs into the cyclodextrin's cavity. The free energy change for the complex formation between chlorpromazine or valethamate and beta -CyD is governed by the enthalpy term and not by the entropy term which controls the surfactant- beta -CyD interactions.