2. OPHTHALMIC DRUG DELIVERY SYSTEM
• Absorption of ophthalmic drugs across the corneal membrane is a
diffusion process and adsorption depends to a large extent on:
1. Physicochemical properties of permeating molecule.
2. Drainage and output of tears.
• If the drug has short half life, the problem becomes more complicated.
Frequent dosing of large doses of such drug is necessary to achieve the
therapeutic objective which often results in corresponding increase in
local irritation and systemetic side effects.
• One of the approach is to improve drug effectiveness is to prolong its
contact with corneal surface.
3. OPHTHALMIC DRUG DELIVERY SYSTEM
• Highly viscous preparation like suspension and ointment are
intended to achieve this purpose but do not offer the amount of
control desired.
• Continuous delivery of drugs in controlled manner can overcome
most of these problems.
• The best known system is ocular insert or ocusert developed to
deliver pilocarpine in the treatment of glaucoma. Available in two
release form 20 and 40 microgram/hr, the system provides relief for
7 days ( insertion below the cornea) in contrast to eye drops which
are required to be instilled 3 to 4 times a day.
4. OPHTHALMIC DRUG DELIVERY SYSTEM
• The system is basically a thin, flexible wafer, composed of drug
reservoir core surrounded on either sides by rate controlling
membranes of ethylene-vinyl acetate copolymer.
