Hydroxypropylcyclodextrins in parenteral use. I: Lipid dissolution and effects on lipid transfers in vitro

Hydroxypropyl ethers of cyclodextrins form water-soluble inclusion complexes with lipids. Of the three hydroxypropylcyclodextrins examined, hydroxypropyl-alpha-cyclodextrin had limited specificity for phospholipids, and hydroxypropyl-beta-cyclodextrin had limited specificity for cholesterol, and hydroxypropyl-gamma-cyclodextrin was nonspecific. The formation of inclusion complexes was found to be a fast and reversible process in which complexation of cholesterol did not inhibit its oxidation by cholesterol oxidase, and cholesterol of the erythrocyte membrane could be exchanged within a minute for cholesteryl methyl ether which was in the inclusion complex. Thus, hydroxypropylcyclodextrin in the circulation may catalyze the transport of lipids in the direction of equilibrium distribution.