Systemic Absorption of Topical Ocularly Applied Epinephrine and Dipivefrin

The systemic absorption of two drugs, epinephrine and dipivefrin hydrochloride, was determined to be from 55% to 65% of the ocularly applied dose. Although dipivefrin is much more readily absorbed into the eye than epinephrine, the systemic absorption of the two drugs was similar. After ocular treatment, the drugs were slowly absorbed into the body over a period of several hours. The metabolism of epinephrine in the body did not appear to be different whether the drug was applied ocularly or injected intravenously. The metabolism of dipivefrin showed some difference depending on route of administration. The tissue distribution of radioactive material after ocular treatment with epinephrine tagged with carbon 14 was quite different than that observed after intravenous treatment. A major pathway for systemic absorption of ocularly applied material appears to be through the walls of the gastrointestinal tract.