These are the different drug delivery systems which are used for the ocular therapy
Ocular drug delivery
OCULAR DRUG DELIVERY SYSTEM
PRESENTED BY: SOMNATH NAVGIRE
M. PHARM II: (PHARMACEUTICS)
DEPARTMENT OF PHARMACEUTICAL
SCIENCES, RASHATRASANT TUKDOJI
MAHARAJ NAGPUR UNIVERSITY,
IDEAL OPHTHALMIC DELIVERY SYSTEM
Good corneal penetration.
Prolong contact time with corneal tissue.
Simplicity of instillation for the patient.
Non irritative and comfortable form
Appropriate rheological properties
OCULAR DRUG DELIVERY SYSTEMS
Chemical delivery systems
LIMITATIONS OF CONVENTIONAL
Rapid precorneal elimination
Solution drainage by gravity
Frequent instillation is necessary
Sustained and/or controlled drug
Protect the drug from chemical or
Increasing contact time and thus
Better patient compliance.
Factors Affecting Intraocular Bioavailability:
1. Inflow & Outflow of Lacrimal fluids.
2. Efficient naso-lacrimal drainage.
3. Interaction of drug with proteins of Lacrimal fluid.
4. Dilution with tears.
5. Limited and poor corneal permeability
NOVEL OCULAR DRUG DELIVERY SYSTEM
To prolong the pre ocular retention
To reduce the frequency of administration
To provide controlled, continuous drug delivery
To avoid or minimize the initial drug concentration
peak in the aqueous humour
To avoid periods of under-dosing that may occur
between eye drop instillation.
ENHANCEMENT OF BIOAVAILABILITY
Solution Viscosity Solution Drainage.
Enhances viscosity of the formulation.
Slows elimination rate from the precorneal area and enhance contact
Generally hydrophilic polymers- e. Methyl cellulose, polyvinyl
alcohols, polyacrylic acids, sodium carboxy methyl
cellulose,carbomer is used
A minimum viscosity of 20 cst is needed for optimum corneal
USE OF PENETRATION ENHANCERS: Act by
increasing corneal uptake by modifying the integrity of the
Substances which increases the permeability
characteristics of the cornea by modifying the integrity of
corneal epithelium are known as penetration enhancers.
Modes of actions
By increasing the permeability of the cell membrane.
Acting mainly on tight junctions.
Calcium chelators :
e.g. palmiloyl carnitine, sodium caprate, Sodium dodecyl
Bile acids and salts :
e.g. Sodium deoxycholate, Sodium
taurodeoxycholate, Taurocholic acid
e.g. Benzalkonium chloride
e.g. saponins, Digitonon
Fatty acids :
e.g. Caprylic acid
e.g. Azone, Cytochalasins
Prodrugs enhance corneal drug permeability through modification
of the hydrophilic or lipophilicity of the drug.
The method includes modification of chemical structure of the drug
molecule, thus making it selective, site specific and a safe ocular
drug delivery system.
Drugs with increased penetrability through prodrug formulations are
epinehrine, phenylephrine, timolol, pilocarpine
USE OF MUCOADHESIVES IN OCULAR DRUG
Polymereric mucoadhesive vehicle: Retained in the eye due to
non-covalent bonding with conjuctival mucine.
Mucine is capable of picking of 40-80 times of weight of water.
Thus prolongs the residence time of drug in the conjuctival sac.
• Mucoadhesives contain the dosage form which remains adhered
to cornea until the polymer is degraded or mucus replaces itself.
1. Naturally Occurring Mucoadhesives- Lectins, Fibronectins
2. Synthetic Mucoadhesives-PVA,Carbopol, carboxy methyl
cellulose, cross-linked polyacrylic acid
• Drugs incarporated in to this are
pilocarpine, lidocaine, benzocaine and prednisolone acetate.
Mechanism of mucoadhesion
• The polymer undergoes swelling
• Entanglement of the polymer
chains with mucin on the epithelial
• The un-ionized carboxylic acid
residues on the polymer form
hydrogen bonds with the mucin.
• The water-swellable yet water-
insoluble systems are preferred
Lutrol FC – 127 and
Viscosity increased when
their temperature raised to
Coagulates when its native
pH 4.5 raised by tear fluid to
Gelrite Forms clear gel in the
presence of cations
PHASE TRANSITION SYSTEM
PARTICULATE SYSTEM FOR OCULAR DRUG DELIVERY
For water soluble drugs.
Drug is Dispersed, Encapsulated, or Absorbed
Produced by Emulsion Polymerization
• Chemical initiation, Gamma irradiation, Visible light.
Polymerization is carried out by :
Emulsifier stabilizes polymer particle
Polymer used are Biodegradable.
E.g. :- Nanoparticle of Pilocarpine enhances Mitotic
response by 20-23%.
Advantages of nanoparticles
• Sustained drug release and prolonged therapeutic activity
• Site-specific targeting
• Higher cellular permeability
• Protect the drug from chemical or enzymatic hydrolysis
• Efficient in crossing membrane barriers -blood retinal
• Act as an inert carrier for ophthalmic drugs
• Poly alkyl cyano acrylate(PACA) nanoparticles and
nanocapsules improve corneal penetration of hydrophilic
and lipophilic drugs.
• Poly- ԑ-caprolactone(PECL) nanocapsules increase ocular
penetration of lipophilic drugs such as
• Vesicle composed of phospholipid bilayer enclosing aqueous
compartment in alternate fashion.
• Biodegradable, Non-toxic in nature.
• Types :1.MLV
2.ULV-SUV(upto 100 nm)
LUV(more than 100 nm)
• Polar drugs are incorporated in aqeous compartment while
lipophilic drugs are intercalated into the liposome
• Phospholipids used- Phosphotidylcholine, Phosphotidic
acid, Sphingomyline, Phosphotidyleserine,Cardiolipine
• Drugs delivered intact to various
• Liposomes can be used for both
hydrophilic and hydrophobic drug.
• Possibility of targeting and
decrease drug toxicity.
• The size, charge and other
characteristics can be altered
according to drug and desired
• Their tendency to be uptaken by
• They need many modification
for drug delivery to special
• Cost .
Degradation and Drug Release Of
Niosomes are non-ionic surfactant based
multilamellar(>0.05µm),small unilamellar(0.025-0.05µm) or large
unilamellar vesicles(>0.1µm) in which an aqueous solution of
solute(s) is entirely enclosed by a membrane resulted from
organization of surfactant macromolecules as bilayers
STRUCTURAL COMPONENTS USED
• Surfactants (dialkyl polyoxy ethylene ether non ionic surfactant)
•The vesicle suspension being water based offers greater patient
compliance over oil based systems
•Since the structure of the niosome offers place to accommodate
hydrophilic, lipophilic as well as ampiphilic drug moieties, they can
be used for a variety of drugs.
•The characteristics such as size, lamellarity etc. of the vesicle can be
varied depending on the requirement.
•The vesicles can act as a depot to release the drug slowly and offer a
•They are osmotically active and stable.
•They increase the stability of the entrapped drug
•Improves therapeutic performance of the drug by protecting it from
the biological environment and restricting effects to target cells,
thereby reducing the clearance of the drug.
• Physical instability, Aggregation, Leaking of entrapped drug,
• The vesicle formation takesplace not only just by association of
phospholipids but also by amphiphilic molecular association
• Since many drugs are also amphiphiles, they can form the
• Drug metabolism can be decreased
• Controled release profile can be achieved
• Soluble surface active agents when added in critical amount to
vesicular dispersion leads to solubilization or breakdown of
vesicles & translates them into mixed micellar systems
• e.g: Egg yolk phosphatidyl choline liposomes by the
addition of non ionic surfactants of poly oxy ethylene cetyl
ether till the lamellar and mixed lamellar coexist
• Minimal opacity imposes no hinderance to vision
• Increased patient compliance
• Zero order release can be easily attained
Advantages of vesicular systems
1. No difficulty of insertion as in the case of ocular inserts
2. No tissue irritation and damage as caused by penetration
3. Provide patient compliance as there is no difficulty of
insertion as observed in the case of inserts
4. The vesicular carriers are biocompatable and have minimum
5. Degradation products formed after the release of drugs are
6. They prevent the metabolism of drugs from the enzymes
present at tear/corneal epithelium interface
7. Provide a prolong and sustained release of drug
Iontophoresis is the process in which direct current drives ions into
cells or tissues.
If the drug molecules carry a positive charge, they are driven into
the tissues at the anode; if negatively charged, at the cathode.
Requires a mild electric current which is applied to enhance
ionized drug penetration into tissue.
Ocular iontophoresis offers a drug delivery system that is
fast, painless, safe, and results in the delivery of a high concentration
of the drug to a specific site.
Ocular iontophoresis has gained significant interest recently due
to its non-invasive nature of delivery to both anterior and posterior
Iontophoretic application of antibiotics may enhance their
bactericidal activity and reduce the severity of disease
Can overcome the potential side effects associated with
intraocular injections and implants.
iontophoresis is useful for the treatment of bacterial keratitis.
Cyclodextrins (CDs) forming inclusion complexes with many guest
molecules. And aqueous solubility of hydrophobic drugs can be
enhanced without changing their molecular structure and their
intrinsic ability to permeate biological membranes.
They increase corneal permeation of drugs and increase ocular
bioavailability of poorly water soluble drugs. Applied in the form of
These are macromolecular compounds made up of a series of
branches around a central core. Their nanosize, ease of preparation,
functionalization and possibility to attach multiple surface groups
provides suitable alternative vehicle for ophthalmic drug delivery.
This system can entrap both hydrophilic and lipophilic drugs into
They can be easily prepared through emulsification method,
easily sterilized, and are more stable and have a high capacity for
The presence of surfactants and co-surfactants in microemulsion
increase the dug molecules permeability, thereby increasing
bioavailability of drugs. they act as penetration enhancers to
facilitate corneal drug delivery
It is consist of pure, hydrophobic drugs (poorly water soluble),
suspended in appropriate dispersion medium..
It offer advantages such as more residence time and avoidance of
the high tonicity created by water-soluble drugs, their performance
depends on the intrinsic solubility of the drug in lachrymal fluids
after administration. Thus, they controlled its release and increase
Ocular Control Release System: Ophthalmic Inserts
Definition:- Solid or Semisolid in nature,
- Placed in lower Fornix
- Composed of Polymeric vehicle containing drug.
Desired Criteria For Control Release Ocular Inserts.
Sterility Stability Ease of mfg.
1. Accurate dosing.
2. Absence of preservative.
3. Increase in shelf life due to
absence of water.
• 1. Perceived by patient as foreign body.
• 2. Movement around the eye.
• 3. Occasional loss during sleep or
while rubbing eyes.
• 4. Interference with vision.
• 5. Difficulty in placement & removal.
Ophthalmic inserts are solid devices intended to be placed in
the conjunctival sac and to deliver the drug at a comparatively
Increased ocular permeation with respect to
standard vehicles, hence prolonged drug activity
and a higher drug bioavailability;
Accurate dosing -theoretically, all of the drug is
retained at the absorption site;
Capacity to provide, in some cases, a constant rate of drug
Flexible, oval inserts
Consists of a medicated core reservior prepared out of hydrogel
polymer sandwiched between two sheets of transperant
lipophilic,rate controlling polymer like ethylene/vinyl acetate
CONTACT LENS :
The most widely used Material is poly-2-hydroxyethylmethacrylate.
Its copolymers with PVP are used to correct eyesight , hold and
Controlled release can be obtained by binding the active ingredient
via biodegradable covalent linkages.
SOLUBLE OCULAR INSERTS
It is a sterile ophthalmic insert use in treatment of dry eye
The insert is composed of 5mg of HPC in rod-shaped form about
1.27 mm diameter by about 3.5 m long
It is made up of counter disc with convex front & concave back
surface in contact with eye ball.
Composition: silicon based pre polymer
Hydrophillic or hydrophobic.
• COLLAGEN SHIELDS
• Collagen is the structural protein of bones, tendons, ligaments and
• skin and comprises more than 25% of the total body protein in
Collagen shields have been used in animal model and in
humans (eg. Antibiotics, antiviral etc.,) or combination of these
drugs often produces higher drug concentration in the cornea and
aqueous humor when compared with eye drops and contact lens
• They are manufactured from porcine scleral tissue, which bears a
collagen composition similar to that of hu-man cornea.
• They are hydrated before being placed on the eye and the drug is
loaded with the collagen shield simply by soaking it in the drug
• They provide a layer of collagen solution that lubricates the eye.
Micro needle used to deliver drug to posterior segment as an
alternative to topical route.
It shows excellent in vitro penetration into sclera and rapid
dissolution of coating solution after insertion. In-vivo drug level was
found to be significantly higher than the level
observed following topical drug administration.
To deliver anti-infective, corticosteroids and anesthetic product to
achieve higher therapeutic condition intraocularly, FDA approved
intraocular Injections includes miotics, viscoelastics, and anti-viral
agents for intravitreal injection
It employed to extend the release in ocular fluids and tissues
particularly in the posterior segment. It may be biodegradable and
With implants, the delivery rate could be modulated by varying
Implants can be in the form of solid, semi-solid or particulate based
delivery systems. These implants have been applied in the treatment of
diseases affecting both anterior and posterior segments of the eye.
Implant containing gancyclovir or, anti-neoplastic agents is release
drug over a 5 to 8 months.
• Combination of SAR and SMR Retrometabolic drug design (RMDD)
• Metabolic activation of inactive delivery forms: chemical delivery systems
Alkyl oxime datives oximes(enzymes located in iris-celiary
• Metabolic deactivation of specifically designed active species:soft drugs
Active inactive metabolites
• RMDD represent novel, systemic approach to achieve these goles include
two distinct methods aimed to increase the therapeutic index
SOFT DRUG design
CHEMICAL DELIVERY SYSTEM design
The chemical delivery systems(CDSs)- chemical compounds –
produced by synthetic chemical reaction(s) forming covalent
bonds between the drug(D) and specifically designed ‘carrier ’
and other moieties. At least one chemical bond needs to be
broken for active compound (D) to be released. The release of
active compound from CDSs takes pace by enzymatic or
The basic principle of retrometabolic drug design approaches
is that the drug metabolism considerations should actually be
involved at a very early stage of the design process- not as an
after thought inorder to explain some of the behaviours of the
SAR+SMR=RETROMETABOLIC DRUG DELIVERY
Drug targeting by CDS’s
1.enzymatic physical chemical
2.site specific-enzyme activated
3.receptor based chemical
Drug targeting by soft drugs
1.soft drug analogs
2.activated soft coompounds
3.active metabolite type soft drugs
4.controlled release of endogenous
5.Inactive metabolic approach
The main efforts in ocular drug delivery is to prolong the residence time of
The development of ophthalmic drug delivery systems is easy because we
can easily target the eye to treat ocular diseases
the eye has specific characteristics such as eye protecting mechanism, which
make ocular delivery systems extremely difficult.
The most widely developed drug delivery system is represented by the
conventional and non-conventional ophthalmic formulations to polymeric
hydrogels, nanoparticle, nanosuspensions, microemulsions, iontophorosis and
In future an ideal system should be able to achieve an effective drug
concentration at the target tissue for an extended period of time, while
minimizing systemic exposure and the system should be both comfortable and
easy to use.
• Ophthalmic drug delivery system: Challenges and approaches
PB Patel, DH Shastri, PK Shelat, AK Shukla
Controlled drug delivery – Concepts and Advances, by S.P. Vyas and Roop K.
Khar, page no.: 383 – 410.
Ansel’s Pharmaceutical dosage forms and drug delivery systems, by Loyd V.
Allen, Nicholas G. Popovich and Howard c. Ansel page no.: 661 – 663.
Advances in Controlled and Novel drug delivery, edited by N.K. Jain, page no.:
219 – 223.
. http://www.pharmainfo.net/reviews/recent advances in opthalmic drug delivery
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