opthalmic drug delivery system

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Drug delivery to eye

• By
• shiva
• B.pharmacy

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Introduction

• Definition 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.
• Conventional ophthalmic dosage forms (solutions,
  suspensions, ointments, etc) after instillation
  into the eye, are rapidly drained away from the
  ocular cavity due to tear flow and lacrimal nasal
  drainage.
• The newest dosage forms for ophthalmic drug
  delivery are liposomes, nanoparticles
  ,mucoadhesives,ocular inserts.

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• LIMITATIONS OF CONVENTIONAL DRUG DELIVERY
• Solution drainage by gravity
• Frequent instillation is necessary
• Conjuctival absorption
• ADVANTAGES OF AVANCED DUG DELIVERY
• Sustained and/or controlled drug release
• Site-specific targeting
• Protect the drug from chemical or enzymatic
  hydrolysis
• Increasing contact time and thus improving
  bioavailability
• Better patient compliance.

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Parts of eye
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Mechanism of absorption
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Use of mucoadhesives in ocular drug delivery

• Mucoadhesives contain the dosage form which
  remains adhered to cornea until the polymer is
  degraded or mucus replaces itself.
• Types-
• Naturally Occurring Mucoadhesives- Lectins,
  Fibronectins
• Synthetic Mucoadhesives-PVA ,Carbopol,
  carboxymethylcellulose,cross-linked polyacrylic
  acid
• Drugs incorporated in to this are pilocarpine,
  lidocaine, benzocaine and prednisolone acetate.

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Mechanism of mucoadhesion

• The polymer undergoes swelling in water,
• Entanglement of the polymer chains with mucin on
  the epithelial surface.
• The un-ionized carboxylic acid residues on the
  polymer form hydrogen bonds with the mucin.
• The water- swellable yet water-insoluble systems
  are preferred

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Ocular inserts

• Sterile preparations, with a thin, multilayered,
  drug-impregnated, solid or semisolid consistency
  devices placed into cul-de-sac or conjunctival
  sac.
• Advantages
• Increasing contact time and thus improving
  bioavailability.
• Providing a prolong drug release and 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.

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Desired criteria for ocular inserts

• Ease of handling and insertion
• Lack of expulsion during wear
• Reproducibility of release kinetics (Zero-order
  drug delivery)
• Applicability to variety of drugs
• Non-interference with vision and oxygen
  permeability.
• Sterility.
• Ease of manufacture

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Non erodible

• 1. Ocusert is a multilayered structure
  consisting of a drug containing core surrounded
  on each side by a layer of copolymer membranes
  through which the drug diffuses at a constant
  rate.
• The rate of drug diffusion is controlled by
• The polymer composition
• The membrane thickness
• The solubility of the drug
• e.g. The Ocusert Pilo-20 and Pilo-40 Ocular
  system
• Designed to be placed in the inferior cul-de-sac
  between the sclera and the eyelid and to release
  pilocarpine continuously at a steady rate for
  7days.
• - consists of (a) a drug reservoir, pilocarpine
  (free base), and a carrier material, alginic
  acid (b) a rate controller ethylene vinyl
  acetate (EVA) copolymer membrane.

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• 2. Contact lens
• Presoaked Hydrophilic lens.
• Drug Release within 1st 30 Min.
• Alternate approach incorporate drug either as
  soln or suspension .e.g. Pilocarpine.
• Release rate is up to 180 hr.

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Erodible

• 1. SODI (soluble ocular drug insert)

• Small water soluble made of soluble synthetic
  polymers.
• Composition Acryl amide, Vinyl Pyrolidone,
  Ethylacrylate.
• Weight 15-16 mg.
• In 10-15 sec Softens
• In 10-15 min. turns in Viscous Liquids
• After 30-60min. Becomes Polymeric Solution.
• ADVANTAGES

• Single SODI application replaces 4-12 eye drops
  Instillation, or 3-6 application of Ointments.
• Once a day treatment of Glaucoma.

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• 2.Lacrisert
• Sterile, Rod Shaped device.
• Composition HPC.
• Weight5mg,
• DimensionDiameter12.5mm, Length3.5mm
• Use-Dry eye treatment.
• 3.Minidisc
• It is made up of counter disc with Convex front
  Concave back surface in contact with eye ball.
• 4-5mm in diameter.
• Composition Silicon based polymer.
• Drug release upto170 hr.

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Liposomes

• 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)
• 3. LUV(more than 100 nm)
• Polar drugs are incorporated in aqueous
  compartment while lipophilic drug are
  intercalated into the liposome membrane.
• Phospholipids used- Phophotidylcholine,
  Phosphotidic acid, Phosphotidyleserine,Cardiolipi
  ne

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• ADVANTAGES
• Drugs delivered intact to various body tissues.
• 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 tissue.
• DISADVANTAGES OF LIPOSOMES
• They need many modification for drug delivery to
  special organs.
• Cost .

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Nanoparticles

• For water soluble drugs
• Size is about 10-1000 nm
• Drug is dispersed, encapsulated or absorbed
• Produced by emulsion polymerization
• Polymerization is carried out by chemical
  initiation, or by irradiation with gamma rays,
  uv or visible light.
• Polymer used are biodegradable.
• E.g Nanoparticles of pilocarpine have shown an
  enhanced miotic response by about 22-23.

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• 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 barrier
• Act as an inert carrier.

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THANK YOU Shiva.pharmacist_at_gmail.com