Aditya.ocular Dds

8/6/2019 Aditya.ocular Dds

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FORMULATION OF OCULAR DRUG

DELIVERY SYSTEMSubmitted To:

Mr. Hemant K.S.Y

Dept. of Pharmaceutics

JSSCP, Mysore.

Submitted By:

Acharya Aditya.A

M.Pharm 1st Year(I.P)

JSSCP,Mysore.


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OCULAR DRUG DELIVERY SYSTEMS

REQUSITES OF CONTROLLED OCULAR DELIVERY

SYSTEMS

To overcome the side effects of pulsed dosing (frequentdosing and high concentration) produced by conventional

systems.

To provide sustained and controlled drug delivery.

To increase the ocular contact bioavailability of drug by

increasing corneal contact time.


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To provide targeting within the ocular globe so as to prevent

the loss to other ocular diseases.

To overcome the protective barriers like drainage, lacrimation

and diversion of exogenous chemicals into systemic circulation

by conjunctiva.

To provide comfort and patient compliance to the patient and

yet improve the therapeutic performance of the drug over

conventional systems.

To provide better housing of the delivery system in the eye so

as the loss to other tissues besides cornea is prevented.


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NEW TRENDS

Ocular drugs and delivery systems are currently undergoing a

process of design optimization due to inherent physiological

and anatomical constraint of the eye leading to limitedabsorption of topically applied drugs.


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Two major approaches are being undertaken to improve

topical delivery of drugs which are,

A) Approaches to prolong the contact time of the drug with

corneal surface.

B) Approaches to enhance corneal permeability either by,

mild or transient structural alteration of corneal epithelium

by modification of chemical structure of the drug molecules.


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The recent formulations that are currently being explored

include:

1. Polymeric solutions

2. Phase transition systems

3. Mucoadhesives/ Bioadhesives dosage form4. Collagen shields

5. Pseudolatices

6. Ocular penetration enhances

7. Ocular iontophoresis and

8. Various ocular drug delivery devices.


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POLYMERIC SOLUTIONS

Addition of polymers to the eye drop solution increases the

corneal penetrations of drug.

This is due to increase in tear viscosity, which decreases rapid

initial drainage rate, increases the corneal contact time and

thus sustains to some extant the initial tear concentration of

the drug.

E.g. methylcellulose, polyvinyl pyrrolidone.


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PHASE TRANSITION SYSTEMS

These are liquid dosage forms which shift to the gel or solid

phase when instilled in the cul-de-sac.

E.g. Lutrol FC-127 and Poloxamer whose viscosity increases

when its temperature is raised to 370

C. Cellulose acetate phthalate(CAP) serves as good sustained

release material for ophthalmic use.

Advantage:

withstand sterilization by autoclaving. Disadvantages:

The surfactant properties and low pH of CAP, limits their use.


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MUCOADHESIVE/BIOADHESIVE DOSAGE FORMS

If the polymer adheres to the mucin, the interaction is

referred to as mucoadhesion.

These systems can be either polymeric solution or

microparticle solution.

They are retained in the cul-de-sac through adhesive bondsestablished with the mucins or the epithelium thus increasing

the corneal contact time.


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But, water soluble polymers have a short half-life.

The corneal contact time is rate limited by dissolution ofpolymers with cross linked mucoadhesives.

E.g. polycarbophil, is an acrylic acid based polymer lightly

crosslinked and able to pickup water approximately 100 timesit sweight at neutral pH.


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These polymers are usually macromolecular hydrocolloids

with numerous hydrophilic functional groups.

These groups are, carboxyl, hydroxyl, amide and sulphate.

They establish electrostatic and hydrophobic interactions and

hydrogen bonding with the underlying surface.

A good bioadhesive should exhibit a near zero contact angle

to allow maximal contact with the mucin coat.


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The structural factors like chain flexibility and molecularweight also influence the bioadhesion.

To diffuse and penetrate into mucin layer, flexibility in chain ofpolymer is required.

The entanglement with mucin coat increases the adhesivestrength of polymer.

Increase in molecular weight to a critical value, increases thebioadhesiveness.


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COLLAGEN SHIELDS

Collagen is the structural protein of bones, tendons, ligaments, and

skin and comprises more than 25% of the total body protein in

mammals.

This protein, which is derived from intestinal collagen, has several

biomedical applications.

Bloomfield et al used of collagen inserts as tear substitutes and as

delivery systems for gentamycin.

They compared the levels of gentamycin in tears, cornea, and sclera

of the rabbit eye after application of a collagen insert, drops, anointment.

After 3 hrs, they found that the collagen insert gave the highest

concentration of gentamycin in the tear film and in the tissue.


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Other treatments using collagen shields impregnated with

gentamicin and dexamethasone have been described.

Some drawbacks of these devices:

a) To apply the collagen shield, the cornea is anaesthetized

while the physician uses a blunt forceps to insert the

hydrated or unhydrated shield.

b) Contrary to medicated contact lenses, collagen shields oftenproduce some discomfort and interfere with vision.


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A new preparation referred to as collasomes consists of small

pieces (1 mm x 2 mm x 0.1 mm) of collagen suspended in a

1% methylcellulose vehicle.

Kaufman and co-workers recently reported that collasomes

provide the same therapeutic advantages of the shields (high

and sustained levels of drugs and/or lubricants to the cornea).


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PSEUDOLATICES

New class of polymeric colloidal dispersion and film forming

agents used for topical applications for sustained drug activity.

Organic solutions of polymers is dispersed in an aqueousphase to form a o/w type of emilsion subsequently using

appropriate means, i.e. by applying vacuum, or by using

controlled temperature.

Water is removed partially to an extent that residual water is

sufficient enough to keep polymeric phase discrete and

dispersed.


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Such dispersions are referred to pseudolatices which on

application leave an intact non invasive continuous polymer

film which reserves drug.

The drug from such systems is released slowly over a

prolonged period of time ensuring better ocular availability

and patient compliance by avoiding frequent instillaton of

preparation.


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OCULAR PENETRATION ENHANCERS

They are used to increase the bioavailability of topically

applied peptides and proteins which are poorly absorbed due

to unfavouable molecular size, charge, hydrophilicity as well

as their succeptibility to degradation by peptides in the eye.

Disadvantages: They create the multiple effects on the tissues

and tissue irritation and damage.


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OCULAR IONTOPHORESIS

It is the process in which the direct current derives ions into

call or tissues.

Antibiotics, antifungal, anesthetic agents and adrenergicagents have been tried by this method.


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REFERENCES

S.P. Vyas and R.K.Khar, Controlled Drug Delivery-

Concepts and advances, Pg.no: 384-394

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