Cyclodextrins in ophthalmic drug delivery

Most ocular diseases are treated by topical drug application in the form of aqueous eye drop solutions. Recent studies have shown that cyclodextrins are useful additives in ophthalmic formulations for increasing the aqueous solubility, aqueous stability and bioavailability of ophthalmic drugs, and to decrease drug irritation. However, these studies have also shown that there are some basic differences between ophthalmic administration of cyclodextrins and administration of cyclodextrins via other routes. These differences have induced some limitations in the ophthalmic application of these most recently developed pharmaceutical excipients. The objective of this review is to summarize recent findings and applications of various cyclodextrins in ophthalmic drug delivery. Their mechanism of action in aqueous eye drop formulations is also discussed. Finally, the formulation of a couple of cyclodextrin containing eye drop solutions is described.