The role of xenobiotic transporters in ophthalmic drug delivery.

The eye is a very complex sensory organ consisting of numerous structures to coordinate the function of sight. It has a series of physical and chemical barriers to help maintain its homeostasis, and mediate environmental exposures. Transporters in the eye play a very important role in maintaining homeostasis by facilitating the movement of ions, nutrients and xenobiotics to various tissues in the eye, especially to non-vascular tissues like the lens and cornea. They also ensure proper cell signaling by shuttling neurotransmitters within the retina. Thus, they are expected to play an important role in determining the ocular exposure of drugs and other pharmacotherapeutics. However, the role of ocular transporters in ophthalmic drug delivery and their clinical relevance has not been well characterized. The purpose of the present review is to summarize the current evidence in the literature on ocular drug transporters and their role in ocular drug delivery, with the emphasis predominantly on their role in ocular pharmacokinetics.