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‐α‐cyclodextrin had limited specificity for phospholipids, and hydroxypropyl‐β‐cyclodextrin had limited specificity for cholesterol, and hydroxypropyl‐γ‐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.