Effect of cyclodextrins on topical drug delivery to the eye

Cyclodextrins are oligosaccharides which form a new group of pharmaceutical excipients. Cyclodextrins have been added to aqueous eye drop preparations to solubilize lipophilic water-insoluble drug, to increase the chemical stability of drugs, or to reduce local drug irritation in the eye. Hydrophilic cyclodextrins, such as 2-hydroxypropyl-beta-cyclodextrin, have been shown to be nontoxic to the eye and are generally well tolerated in aqueous eye drop formulations. However, improper formulation of aqueous cyclodextrin containing eye drop solutions can reduce the topical availability of the drug molecule. This paper reviews the effects of cyclodextrins and aqueous cyclodextrin eye drop formulations on the ocular bioavailability of drugs.