rk singh ocular dds

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OCULAR DRUG DELIVERY SYSTEM Presented by RABINDRA KUMAR SINGH M . Pharm 2 nd Sem , Roll.No.-06 DEPARTMENT OF PHARMACEUTICAL SCIENCES DIBRUGARH UNIVERSITY DIBRUGARH-786004

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INTRODUCTION: The ocular drug delivery systems is the specialized dosage forms designed to be instilled onto the topical, intraocular or periocular to the eye or used in conjunction with an ophthalmic device. Conventional topical therapeutic dosage form includes : Solutions, Suspensions, Ointments. Novel ocular drug delivery systems includes: Microemulsions , Nanoparticles, Liposomes, Niosomes , Nanosuspensions , Dendrimers, Implants and Hydrogels . The most commonly employed ophthalmic dosage forms are solutions, suspensions, and ointments. But these preparations when in­stilled into the eye are rapidly drained away from the ocular cavity due to tear flow and lacrimal drainage. To increase ocular bioavailability and retention time on the ocular surface, numerous ophthalmic vehicles such as viscous solutions, suspensions, emulsions, ointments, aqueous gels, and polymeric inserts, have been investigated.

IDEAL OPHTHALMIC DELIVERY SYSTEM: 

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

FACTORS AFFECTING INTRAOCULAR BIOAVAILABILITY: 

FACTORS AFFECTING INTRAOCULAR BIOAVAILABILITY Continual inflow and outflow of lacrimal fluid Drainage of the instilled solution Limited corneal and poor corneal permeability Productive and nonproductive absorption of the drug into cornea and conjuctiva Interaction of the drugs with the proteins of the lacrimal fluid. Metabolism

NOVEL OCULAR DRUG DELIVERY SYSTEM: 

NOVEL OCULAR DRUG DELIVERY SYSTEM OBJECTIVES : 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: 

ENHANCEMENT OF BIOAVAILABILITY Topical bioavailability can be improved by – Maximizing pre-corneal drug absorption Minimizing pre-corneal drug loss VISCOSITY IMPROVER : It Increases drug contact time. generally hydrophilic polymers- e. g cellulose, polyalcohols , polyacrylic acids, sodium carboxy methyl cellulose,carbomer is uses.

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PENETRATION ENHANCER : Act by increasing corneal uptake by modifying the integrity of the corneal epithelium PRODRUGS : modification of chemical structure - selective, site specific BIOADHESIVE POLYMERS : Adheres to the mucin coat covering the conjuctiva and corneal surface of the eye. Thus prolongs the residence time of drug in the conjuctival sac.

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IN SITU FORMING GEL : Liquid upon instillation undergo phase transition in the ocular system to form visco - elastic gel NANOPARTICLES : Provide sustained release and prolonged therapeutic activity after topical administration and the entrapped drug must be released from the particles at an appropriate rate. LIPOSOMES : has an affinity to bind to ocular surfaces, and release contents at optimal rates NOVEL APPROACH IN OCULAR CONTROLLED DRUG DELIVERY

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MICRO PARTICULATES : The drug is released through diffusion, chemical reaction, and polymer degradation. MICROEMULSION : improve permeation across the cornea. PHARMACOSOMES : They show greater stability, facilitated transport across the cornea and a controlled release profile. NIOSOMES : Prevent release their drainage into the systemic pool

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IONTOPHORESIS 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 segment. Requires a mild electric current which is applied to enhance ionized drug penetration into tissue. Can overcome the potential side effects associated with intraocular injections and implants. iontophoresis is useful for the treatment of bacterial keratitis .

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CYCLODEXTRINS : 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 eye drops. DENDRIMERS : 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 their structure.

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MICROEMULSION They can be easily prepared through emulsification method, easily sterilized, and are more stable and have a high capacity for dissolving drugs. 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 NANOSUSPENSIONS It is consist of pure, hydrophobic drugs (poorly water soluble), suspended in appropriate dispersion medium. The technology are utilised for drug components that form crystals with high energy content molecule, which renders them insoluble in either hydrophobic or hydrophilic media. 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 bioavailability.

CONTROLLED RELEASE OCULAR DEVICES: 

CONTROLLED RELEASE OCULAR DEVICES INSERTS: Ophthalmic inserts are solid devices intended to be placed in the conjunctival sac and to deliver the drug at a comparatively slow rate 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 release;

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INSOLUBLE INSERTS OCUSERTS: 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 copolymer membrane. CONTACT LENS : The most widely used Material is poly-2-hydroxyethylmethacrylate. Its copolymers with PVP are used to correct eyesight , hold and deliver drugs. Controlled release can be obtained by binding the active ingredient via biodegradable covalent linkages.

SOLUBLE OCULAR INSERTS: 

SOLUBLE OCULAR INSERTS LACRISERT: It is a sterile ophthalmic insert use in treatment of dry eye syndrome. The insert is composed of 5mg of HPC in rod-shaped form about 1.27 mm diameter by about 3.5 m long MINIDISC: 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.

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COLLAGEN SHIELDS They are manufactured from porcine scleral tissue, which bears a collagen composition similar to that of hu­man 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 solution. They provide a layer of collagen solution that lubricates the eye.

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INTRAOCULAR INJECTIONS 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

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INTRAOCULAR IMPLANTS It employed to extend the release in ocular fluids and tissues particularly in the posterior segment. It may be biodegradable and non-biodegradable. With implants, the delivery rate could be modulated by varying polymer composition. 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 .

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CONCLUSION The main efforts in ocular drug delivery is to prolong the residence time of drugs 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 ocular inserts. 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.

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REFERENCES 1. Lee VHL, Robinson JR: Topical ocular drug delivery: recent developments and future challenges. Journal of Ocular Pharmacology 1986; 2: 67–108. 2. Lang J C. Ocualar drug delivery conventional ocular formulation. Advanced drug delivery review 1995;16:39-43. 3. K.Noriyuki,et.al ; Journal of polymer 2011;3:193-221 4. G.Ripal et.al; Journal of pharmaceutical research 2009;26(5). 5. N.K.Jain , Advances in controlled and novel drug delivery, CBS Publishers and distributors,1 st edition,page no.218-223. 6. http://www.pharmainfo.net/reviews/recent advances in opthalmic drug delivery system.

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