Potential systemic side effects of six common ophthalmic drugs.

Drugs applied topically on the eye are partly absorbed into the eye (possibly 2 to 10%), the remainder can enter the systemic circulation through the conjuctival vessels or from the vessles of the nasolacrimal passages. Drug molecules which enter the stomach and are not transformed into inactive compounds may also enter the blood stream. Systemic reactions to topically applied ophthalmic drugs are shown to be rare and largely preventable.