They are specialized dosage forms designed to be instilled onto the external surface of the eye(topical), administered inside(intraocular) or adjacent(periocular) to the eye, or used in conjunction with an ophthalmic device. The novel approach of drug delivery system in which drug can instill on the cull de sac cavity of the eye is known as ocular drug delivery system. APPROACHES TO IMPROVE OCULAR DRUG DELIVERY: Viscosity enhancer Eye ointments Prodrugs Penetration enhancer Mucoadhesives In-situ gel Nanoemulsion Implants Microemulsion Liposomes Niosomes Nanoparticles

1. Approaches to overcome the barriers
of Ocular Drug Delivery System
By – Sakshi Mishra
M.Pharm 1st year (Pharmaceutics)
Institute of Pharmaceutical Research
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2. OCULAR DRUG DELIVERY
SYSTEMS:
 They are specialized dosage forms designed to be instilled onto the
external surface of the eye(topical), administered inside(intraocular) or
adjacent(periocular) to the eye or used in conjunction with an
ophthalmic device.
 The novel approach of drug delivery system in which drug can instilled
on the cull de sac cavity of eye is known as ocular drug delivery system.
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3. BARRIERS OF OCULAR DRUG DELIVERY SYSTEM:-
 Precorneal constraints:
 Spillage of drug by overflow/solution drainage
 Nasolacrimal drainage
 Tear dilution
 Enzymatic metabolism
 Corneal constraints:
 Outer epithelium(lipophilic)
 Middle stroma(hydrophilic)
 Inner endothelium(lipophilic)
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4. DISADVANTAGES OF CONVENTIONAL OCULAR
DRUG DELIVERY SYSTEM:-
 Less bioavailability
 Protein-binding
 Lacrimation
 Less intimate contact
 Lower residence time
 Patient incompliance
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5. IDEAL CHARACTERISTICS REQUIRED TO
OPTIMIZE OCULAR DRUG DELIVERY SYSTEM:-
 Good corneal penetration
 Prolong contact time with corneal tissue
 Simplicity of installation for the patient
 Non irritative and comfortable
 Appropriate rheological properties
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6. APPROACHES TO IMPROVE OCULAR DRUG DELIVERY:
• Viscosity enhancer
• Eye ointments
• Prodrugs
• Penetration enhancer
• Mucoadhesives
• In-situ gel
• Nanoemulsion
• Implants
• Micro emulsion
• Liposomes
• Niosomes
• Nanoparticles
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7. 1.PENETRATION ENHANCERS:-
 Substances which increases permeability characteristics of the cornea
by modifying the integrity of corneal epithelium are known as
penetration enhancers.
 They basically overcome corneal barriers
MODE OF ACTION-
 Act by increasing the permeability of cell membrane; increase corneal
uptake
 Act mainly on tight junctions exhibited by paracellular pathway.
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8. 2.PRODRUGS:-
 Overcome corneal barrier
 Enhance corneal drug permeability through modification of
hydrophilicity and lipophilicity of the drug.
 Within cornea, the prodrug is either chemically or enzymatically
metabolized to active parent compound.
 Examples of drugs which increase corneal permeability by prodrug are
epinephrine, phenylephrine, pilocarpine etc.
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9. 3. MUCOADHESIVES:-
 Work by increasing the residence time of drug in
conjunctival sac.
 Overcome precorneal barriers.
 Examples- lectins, Carbopol, chitosan etc.
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10. 4. VISCOSITY ENHANCER:-
 Usually added to ophthalmic solutions to increase viscosity, which
corresponds to slower elimination
 Lead to enhance precorneal residence time
 Polymers include polyvinyl alcohol, methylcellulose,hydroxypropyl
cellulose etc.
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11. 5. IN-SITU GEL:-
 They are liquid upon installation, and undergo phase transition in the
ocular cull de sac to form gel.
 Thus prolong residence time and improve ocular bioavailability of
drugs.
 Improve precorneal barrier.
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12. Some novel approaches:
Some of the novel approaches of ocular drug delivery are liposomes,
Niosomes, nanoparticles, nanosuspension, nano emulsion.
They overcome both corneal and precorneal barriers.
1. NIOSOMES
 Niosomes are bilayer structural vesicles made up of non- ionic
surfactant which are capable of encapsulating both lipophilic and
hydrophilic compounds
 when vesicular systems were formed when a mixture of cholesterol and
single alkyl chain non ionic surfactant was hydrated
 Niosomes reduce the systemic drainage and improve the residence
time, which leads to increase ocular bioavailability
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13. 2. LIPOSOMES-
 The behavior of liposomes as an ocular drug delivery system has been
observed to be, in part, due to their surface charge.
 Positively charged liposomes seem to be preferentially captured at the
negatively charged corneal surface as compared with neutral or
negatively charged liposomes.
 It overcome both precorneal and corneal barrier.
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15. 3. NANOPARTICLES-
 These are polymeric colloidal particles, ranging from 10 nm to 1000 nm,
in which the drug is dissolved, entrapped, encapsulated, or adsorbed.
 Encapsulation of the drug leads to stabilization of the drug.
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16. 4. IMPLANTS-
 Implants have been widely employed to extend the release
of drugs in ocular fluids and tissues particularly in the
posterior segment.
 Implants can be broadly classified into:-
 Biodegradable and non degradable implants
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17. 5. OCUSERTS:
Ocular insert (Ocusert) are sterile preparation that prolong residence time
of drug with a controlled release manner and negligible or less affected by
nasolacrimal drainage.
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18. References
 Prausnitz MR, Noonan JS. Permeability of cornea, sclera, and conjunctiva: a
literature analysis for drug delivery to the eye. J Pharm Sci. 1998;87:1479-
1488.
 Doane MG, Jensen AD, Dohlman CH. Penetration routes of topically applied
eye medications. Am J Ophthalmol. 1978;85:383-386.
 Janoria KG, Gunda S, Boddu SH, Mitra AK. Novel approaches to retinal drug
delivery. Expert Opin Drug Deliv. 2007;4:371-388.
 Kaur IP, Smitha R. Penetration enhancers and ocular bioadhesives: two new
avenues for ophthalmic drug delivery. Drug Dev Ind Pharm. 2002;28:353-369.
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