Ointments and Inserts

In an effort to maintain longer contact between the drug and ocular tissue, ointments and inserts have been used.

Ophthalmic ointments tend to keep the drug in contact with the eye longer than suspensions. Most ophthalmic ointment bases are a mixture of mineral oil and white petrolatum and have a melting point close to body temperature. Sometimes anhydrous lanolin is used to take up an ingredient that was dissolved in a small amount of water to affect dissolution. The aqueous solution is incorporated into the lanolin and then the lanolin is mixed with the remaining ointment base ingredients.

Ointments must be nonirritating and free from grittiness so the micronized form of the ingredients is required. Sterile ointments are prepared by first sterilizing all of the individual ingredients and then combining them under aseptic conditions. The prepared ointment is then packaged in a sterile container such as an ointment tube.

Most ointments tend to blur patient vision as they remain viscous and are not removed easily by the tear fluid. Thus ointments are generally used at night as adjunctive therapy to eye drops used during the day. Ophthalmic ointment tubes are typically small holding approximately 3.5 g of ointment and fitted with narrow gauge tips which permit the extrusion of narrow bands of ointment.

Ocular inserts are not compounded but must be manufactured. Ocusert® is a nonerodible device designed to deliver pilocarpine for several days in the treatment of glaucoma. Some inserts are designed to dissolve in tear fluid. These inserts are made of dried polymeric solutions that have been fashioned into a film or rod. An example of this type of insert is Lacrisert® used to treat moderate to severe dry eye syndrome. Inserts are placed in the cul-de-sac between the eyeball and the eyelid. The biggest disadvantage of inserts is their tendency to float on the eyeball, particularly in the morning upon arising.