Prostaglandins and other eicosanoids: their ocular transport, pharmacokinetics, and therapeutic effects

Since prostaglandins (PGs) were originally discovered in the eye in a search for the mediators of the ocular irritative responses, it is not surprising that the first decade of research on the ocular effects of these autacoids concentrated on their potential role in inflammation and other pathological processes. It is clear that PGs, like most other biologically active compounds, can have pathological effects when introduced into the eye in sufficiently high doses. More recent studies indicate, however, that PGs are also involved in the normal physiological processes of the eye, and that some PGs effectively reduce intraocular pressure and may actually moderate rather than mediate ocular inflammation. We must therefore consider the eicosanoids as a new class of potential ocular therapeutic agents. This paper reviews the evidence that these autacoids are actively transported by some tissues, including the ciliary epithelium, and considers the role of such transport processes in the ocular and systemic pharmacokinetics of endogenous eicosanoids and their therapeutically applied prodrugs.