What’s New in Ocular Pharmacology?

What route when?

Three anatomic features determine ocular drug penetration:
1. The cornea - Few topically applied drugs penetrate the cornea. Those that do penetrate do not “reach” the vitreous, choroid, retina, optic nerve or orbit.
2. The blood-ocular barrier prevents most systemically administered drugs from entering intraocular tissues other than the uvea.
3. The avascular structures of the eye - Systemically administered drugs “reach” only vascular areas of the eye.

The Golden Rules of Ophtalmic Drug Delivery

1. Some drugs that are unsafe topically can be given safely via a systemic route
2. Some drugs that are unsafe systemically can be given safely topically
3. Otic and dermatologic preparations should never be used ophthalmically
4. Topical drugs should never be administered subconjunctivally
5. Drugs required in high concentration in the cornea/ conjunctiva are best administered by frequent topical application.
6. Drugs required in high concentration in vascular components of the eye usually are best administered systemically.
7. Increased “dose” of topically applied drugs is achieved by increasing drug concentration; increasing frequency of application; or increasing contact time
8. Systemic absorption of drugs from the conjunctival sac following topical application may result in notable blood concentrations in small patients
9. Ointments increase contact time, provide lubrication, and protect against desiccation
10. Ointments should not be used when corneal rupture is present/likely or prior to ocular surgery
11. Subconjunctival injection permits a portion of the administered drug to bypass the barrier of the corneal epithelium and penetrate transclerally. However, a notable proportion of the injected drug leaks back out the injection tract and is absorbed as if it was administered topically.
12. Always administer one drop
13. Always leave 5 minutes between drops of a different type
14. Always work “up” in viscosity when applying two or more different drops or ointments to the same eye [...]