OCULAR ABSORPTION FOLLOWING TOPICAL DELIVERY

Most ocular diseases are treated with topical application of eyedrops. After instillation of an eyedrop, typically less than 5% of the applied drug penetrates the cornea and reaches intraocular tissues, while a major fraction of the instilled dose is absorbed and enters the systemic circulation. Ocular absorption of topically applied ophthalmic drugs is limited by rapid precorneal drug elimination due to solution drainage and systemic absorption from the conjunctival sac. Another factor that limits ocular absorption is the corneal epithelial barrier. In the eye drugs are distributed from the aqueous humor to intraocular tissues and eliminated mainly via aqueous humor turnover and venous blood flow in the anterior uvea. Because of the publication of several reviews [1-3] on ocular drug absorption this review will focus on the most recent literature.