Ophthalmic therapeutics ointments

In addition to suspensions, pharmaceutical products may be emulsions or foams. In any case, the rheological properties have to be tailored to suit the nature of the apphcation [13]. Therapeutic ointments are usually not very viscous and encounter only moderate shear rates upon application, about 125 s" when gently smeared on with fingers, and about 210 s when smeared on with a spatula [13]. An ophthalmic ointment is usually very soft, with a viscosity of about 20 - 30 mPa s, whereas a medicated ointment needs to be soft enough to apply easily but stiff enough to remain on the area to which it was applied, with a viscosity of about 30 -40 mPa-s [13]. A protective ointment like zinc oxide paste needs to be hard and stiff enough to stay in place where applied, even when moist. 

Therapeutic uses An ophthalmic ointment of the drug is used topically in the eye for the chronic treatment of open-angle glaucoma. The effects may last for up to one week after a single administration. [Note Echothiophate [ek oe THI oh fate] is a newer drug that covalently bonds to acetylcholinesterase. Its use is the same as isoflurophate.]... 

Descemet s membrane, reestablishing stromal deturges-cence. Conservative therapeutic measures may be instituted during this resolution period, including the use of topical 5% sodium chloride drops during the day and 5% sodium chloride ointment instilled into the conjunctival sac at bedtime. Broad-spectrum topical ophthalmic antibiotics may be instituted to protect the compromised cornea from secondary bacterial infection. 

While ophthalmic solutions are by far the most preferred dosage forms, ophthalmic ointments are still being marketed for night time applications and where prolonged therapeutic actions are required. 

Frequent instillation of solution or higher drug concentration is needed to achieve the desired therapeutic response. But this attempt is potentially dangerous if drug solution drained from the eye is systemically absorbed from the nasolacrimal duct. To increase precorneal residence time and ocular bioavailability, different ophthalmic delivery systems such as viscous solutions, ointments, gels, suspensions, or polymeric inserts are used. But because of blurred vision (e.g., ointments) or lack of patient compliance (e.g., inserts), these formulations have not been widely accepted. 

To improve the therapeutic effect of a medicine, one should try to increase the absorption of the active substance. Eye ointments and eye creams stay much longer in the conjunctival sac and on the ocular surface than eye drops. Consequently the active substance is delivered during a longer period of time to the eye. Ointments or creams could be considered as prolonged release dosage forms (depot preparations) for ophthalmic use. Viscous eye drops can... 

Although satisfactory therapeutic results are obtained with usual topical ophthalmic drug (topical ocular solutions and ointments) they present some inconveniences pt. Bioavailability is poor, requiring high doses and repeated applications. 2 . Diffusion of the drug into the bloodstream across de nasal mucosa which is continuous with the conjuntival sac, represents an additional risk of systemic toxicity. (Chang and Lee, 1987, Salminen,1990). 

Cyclosporine A appears to be effective and well tolerated. Two distinct therapeutic effects of Cyclosporine A ophthalmic ointment were observed, when used BID in dogs with KCS Increased tear production in most cases and improved ocular surface lesions. 

---