21-11-2012, 01:54 PM
OCULAR DRUG DELIVERY SYSTEM
OCCULARDRUGDELIVERYSYSTEM.ppt (Size: 718.5 KB / Downloads: 191)
INTRODUCTION
Ophthalmic preparation
Applied topically to the cornea, or instilled in the space between the eyeball and lower eyelid
Solution
Dilutes with tear and wash away through lachrymal apparatus
Administer at frequent intervals
Suspension
Longer contact time
Irritation potential due to the particle size of drug
Ointment
Longer contact time and greater storage stability
Producing film over the eye and blurring vision
ADVANTGES
Increase ocular residence, hence, improving bioavailability.
Possibility of providing a prolonged drug release and thus a better efficacy.
Lower incidence of visual and systemic side effects.
Increased shelf life with respect to aqueous solutions.
Exclusion of preservatives, thus reducing the risk of sensitivity reactions
MUCOADHESIVE DOSAGE FORMS
The capacity of polymer to adhere to mucin coat forms the basis of mucoadhesion.
These system significantly prolong the drug residence time since clearance is controlled by rate of mucus turn over.
Mucoadhesive polymers are usually macromolecular hydrocolloids which establishes electrostatic, hydrophobic interaction & hydrogen bonding with the underlying surface.
It should exhibit a near zero contact angle to allow maximum contact with the mucin.
Soluble ophthalmic inserts
They are the oldest class of the ophthalmic inserts.
They don’t need to be removed from their site of application.
Here, the drug is absorbed by soaking the insert in a solution containing the drug, drying and re-hydrating it before use.
The amount of drug loaded will depend upon the amount of binding agent, concentration of the drug solution and duration of the soaking.
Osmotic inserts
There are two types of osmotic inserts :
In first type, drug with or without an additional osmotic solute dispersed in a polymeric matrix.
In second type, the drug and the osmotic solute are placed in two separate compartments, the drug reservoir being surrounded by an elastic impermeable membrane the osmotic solute reservoir by a rigid, semi-permeable membrane.
The tear fluid diffuse into peripheral deposits through the semipermeable membranes, wets them and thus generates hydrostatic pressure by which the drug is extruded.
Here, zero order drug release profile is achieved.