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Ocular inserts : 

Ocular inserts G. Umamaheswara Rao

contents : 

contents Introduction Ophthalmic inserts Advantages & disadvantages Types of polymers used Classification of ophthalmic inserts Evaluation of ophthalmic inserts

Introduction : 

Introduction The conventional ocular dosage forms for the delivery of drugs are 1 – Eye drops (solutions, suspensions) Ophthalmic ointments The main drawback of these dosage forms is poor bioavailability and rapid pre-corneal elimination of drugs. These are mainly due to Conjunctival absorption Induced lacrimation Blinking reflex low corneal permeability normal tear turn over rapid solution drainage by gravity

Slide 4: 

Because of this poor ocular bioavailability, many drugs are applied in high concentration. This cause both ocular and systemic side effects2. In order to overcome the constraints placed by these conventional ocular therapies viz. short residence time pulsed dosing of drug frequent installation large drainage factor Newer ocular drug delivery systems are being explored to develop extend duration and controlled release strategy.

Recent trends : 

Recent trends The following recent trends are in existence3 : Membrane bond ocular inserts Mucoadhesive dosage forms Collagen shields Soft contact lenses, implants Filter paper strips Phase transition systems Nanoparticles Ocular iontophoresis, pumps

What are ocular inserts? : 

What are ocular inserts? These are mainly sterile preparations and are thin, multilayered, drug impregnated, solid or semisolid consistency devices placed into cul-de-sac or conjunctival sac 1,4 Objective of ophthalmic inserts The main objective is to increase the contact time between the preparation and conjunctival tissue to ensure a sustained release suited to topical or systemic treatment

Advantages : 

Advantages Increasing contact time and thus improving bioavailability possibility of providing a prolonged drug release an thus a better efficacy reduction of systemic side effects and thus reduced adverse effects reduction of the number of administrations and thus better patient compliance

Slide 9: 

The desired criteria for a ophthalmic inserts are – Ease of handling and insertion lack of expulsion during wear zero order drug release applicability to variety of drugs non-interference with vision and oxygen permeability sterility stability ease of manufacture

Types of polymers : 

Types of polymers Polymers used in the formulation of ocular inserts are cellulose polymers: hydroxy ethyl cellulose (HEC) hydroxypropyl methyl cellulose (HPMC), hydroxypropyl cellulose (HPC), ethyl cellulose (EC), methyl cellulose (MC) Polyvinyl alcohol hyaluronic acid polyethylene oxide Collagen Eudragit poly lactic acid or poly glycolic acid Alginate& its derivatives

Classification of ophthalmic inserts : 

Classification of ophthalmic inserts

Insoluble ophthalmic inserts : 

Insoluble ophthalmic inserts The first two classes (Diffusion and osmotic systems) are reservoir type of systems. The reservoir contain either a liquid/ gel/ colloid/ solid matrix or a carrier – containing drug homogenously or heterogeneously dispersed or dissolved there in The third class including contact lenses

Diffusion inserts : 

Diffusion inserts The diffusion systems composed of a central reservoir of drug enclosed in specially designed semi permeable or microporus membranes, which allow the drug to diffuse from reservoir at determined rate. Here the mechanism of drug release is diffusion controlled The lachrymal fluid enters through the membrane and create some internal pressure which drive the drug out of reservoir

Osmotic inserts : 

Osmotic inserts Osmotic inserts generally composed of two distinct compartments Drug is placed in one compartment and osmotic solute is in another compartment ,which is sandwiched between the rate controlling membrane Osmotic solutes: tartaric acid, sodium chloride, sodium sulfate, sorbitol, mannitol The tear fluid diffuse into osmotic compartment inducing an osmotic pressure due to which drug diffuses

Soft contact lenses : 

Soft contact lenses These are made up of covalently cross linked hydrophilic or hydrophobic polymers that forms a three dimensional network or matrix capable of retaining water, aqueous solution or solid components When a hydrophilic contact lens soaked in a drug solution, it absorbs the drug but does not give a delivery as a precise as that provided by other insoluble ophthalmic systems The drug release from this system is very rapid at the beginning but then declines exponentially with time The release rate can be decreased by incorporating the homogenously during the manufacture or by adding a hydrophobic component

Soluble ophthalmic inserts : 

Soluble ophthalmic inserts Soluble inserts correspond to the oldest class of ophthalmic inserts. This type of inserts entirely soluble so that they do not need to be removed from the site of application. The amount of drug loaded will depend upon the amount of binding agent, concentration of drug solution into which the insert is soaked and duration of soaking. The release of drug from this type of inserts is due to the penetration of tear fluid into the inserts that induces high release rate of drug by diffusion and forms a gel layer around the core of insert

Bioerodible ophthalmic inserts : 

Bioerodible ophthalmic inserts The Bioerodible inserts composed of homogeneous dispersion of a drug which can be included in or not included in the hydrophobic coat made of Bioerodible polymers, which is impermeable to the drug. The drug release from such a system is due to the contact of the device with the tear fluid , including a superficial bioerosion of the matrix.

Slide 18: 

Polymeric ocular inserts

Evaluation of ophthalmic inserts : 

Evaluation of ophthalmic inserts Thickness of film Drug content uniformity Uniformity of weight IN vitro drug release In vivo drug release Accelerated stability studies Test for sterility

Slide 20: 

REFERENCES: 1. Banker. Rhodes., Modern pharmaceutics,Fourth edition,Revised&Expanded,vol#121,1996: 451-469 2.Lee V.H.L, and Robinson J.F, “Review: Topical ocular drug delivery; recent developments and future challenges”. J. Ocul. Pharmacol., 1976; 3. Davis J.L, Gilger B.C, Robinson M.R., Novel approaches to ocular drug delivery. 2004: 195-205 4.Rathore K.S, Nema R.K., “Review : ocular insets.,” Int.J.pharmTech res.2009, 1(2): 164-169

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