Route of absorption of drug and ointment after application to the eye.

Chloramphenicol, tetracycline hydrochloride, sodium sulfacetamide, and fluorescein sodium prepared in both aqueous solutions and ointments were placed in the conjunctival sac of humans. Each drug soon was tasted in the back of the mouth with no difference being noticed with the use of aqueous solution or ointment. Tetracycline and fluorescein studies showed that systemic absorption were similar regardless of whether solution or ointment were used. Furthermore, it was found that the ointment passed through the lacrimal drainage system and into the nose and throat. The ocular contact time of ointment with the eye is greater than that of water, and ointment is much more slowly absorbed via the lacrimal drainage system. Both the drugs and the ointment base applied topically to the eye travel through the nasolacrimal system as the way of elimination when given in the small volumes that are held by the conjunctival sac.