DEPARTMENT OFINDUSTRIAL PHARMACY A SEMINAR ON OCCULAR DRUG DELIVERY SYSTEM SONAM M.GANDHI FIRST M.PHARM
Introduction A drug delivery system ideally should deliver a specified amount of medication to site of action at an appropriate time and date. Novel ocular drug delivery system are designed in order to over come various drawbacks of conventional medications and having improved patient convenience and better therapeutic efficacy. Ocular administration of the drug is primarily associated with need to treat ophthalmic diseases. Systemic action by using eye as a portal is generally avoided in order to prevent the risk of eye damage from high blood concentration of drug not intended for eye.
EVALUATION OF OCULAR DELIVERYSYSTEM The conventional ocular dosage forms for the delivery of drugs are:i. Eye drops,ii. Eye ointments andiii. Eye suspension.
Requisites of controlled ocular deliverysystem:- To over come the side effects of pulsed dosing (frequent dosing and high concentration) produced by conventional dosage form. To provide sustained and controlled drug delivery . To provide comfort and compliance. To provide prolonged drug release. To increase the ocular bioavailability of drug by increasing corneal contact time. This can be achieved by effective coating or adherence to corneal surface.
Approaches made towards optimization of ocular delivery system:-1) Improving ocular contact time.2) Enhancing corneal permeability.3) Enhancing site specificity.
The following recent trends of dosage forms are in vogue:-1. Controlled ocular delivery system: i. Polymeric solution ii. Phase transition system iii. Mucoadhesive / bioadhesive dosage form iv. Collagen shields v. Pseudolatics vi. Ocular penetration enhancers vii. Ocular ion phoresis.
2. Ocular drug delivery devices: 1)Matrix type drug delivery systems. 1. Hydrophilic soft contact lenses 2. Soluble ocular inserts 3. Scleral buckling materials. 2)Capsular type drug delivery system. 1. Ocuserts and releated devices 2. Implantable silicone rubber device 3)Implantable drug delivery pumps. 1. Osmotic mini pump and implantable infusion system 4)others 1. Ocufit and lacrisert 2. Minidisk ocular therapeutic system 3. New ophthalmic delivery system.
1.Controlled ocular delivery system I. Polymeric solution : The addition of polymers like methyl cellulose, poly vinyl alcohol, hydroxyl propyl methyl cellulose and poly vinyl pyrolidine to the eye drop solutions increases the corneal penetration of drug . ll. Phase transition system : These are the liquid dosage forms which shift to the gel or solid phase when instilled into the cul-de-sac. There are three types of phase transition system : a. Temperature dependent. b. PH triggered. c. Ion activated.
III. Mucoadhesive / Bioadhesive dosage form: Any polymer solution or microparticle suspension placed in the eye first encounter mucin at the cornea and conjunctival surface. This polymer adheres to mucin, t he interaction reffered to as mucoadhesion. mucoadhesives polymer are usually macromolecular hydrocolloides with numerous hydrophilic functioal groups. These groups are – COOH, -OH, CONH2 and SO4²¯. A good bioadhesive should exhibit a near zero contact angle to allow maximal contact with mucin coat.
IV. COLLAGE SHIELDS : Collagen is the structural proteins of the bones, tendons ligaments and skin and comprises more then 25% of total body protein in mammals. Collagen is the main constituents of food grade gelatin and derived from intestinal has several biomedical application.V. Pseudolattices : Are a new class of polymeric colloidal dispersions and films foaming agents used for topical application into the animal’s and the human being used for sustaining the drug activity in vivo
Vi Occular penetration enhancers: like actin filament inhibitors, surfactants inhibitors, bile salts, chelators and other compounds have been used to increase the bioavailability of topically applied peptide and protiens which are otherwise poorly absorbed due to unfavourable unfavourable molecular size, charge, hydrophilicity.Vii Occular iontophoresis: Is a process in which the direct current drivse ions into the cell or tissue.
2. CONTROLLED DRUG DELIVERY DEVICES.A) MATRIX-TYPE DRUG DELIVERY SYSTEM:i. Hydrophilic soft contact lenses: Are easy to fit and tolerated and rapidley tolerance, hydrophilic soft contact are more popular for correction of hydrogels like PHP copolymer. The ability of available disposable soft contact lenses to absorb various ocular therapeutic agents and release them. After a 2hr or 4hr presoaking time, they measured the amount of drug released into fresh saline baths for upto 3hr.ii. Soluble ocular inserts: Are thin, elastic, oval plates and made from polymers and co-polymers of polyacrylamide, ethylacrylate and vinyl pyyrolidone. When soluable ocular inserts inserted into a conjunctivl sac, it absorbs tears rapidly, swells and dissolves in about 30-90min releasing the active subsance in a controlled manner.iii. Scleral buckling materials: Are used in retinal detachment surgery as they cause postoperation. So to prevent this complication, scleral buckling matrials can be made to absorb an antibiotic. Two common scleral buckling materials, gelatin film and solid silicon rubber.
B) CAPSULAR TYPE DRUG DELIVERY SYSTEM:i. Ocuserts and related devises: The system consists of pilocarpine and alginic acid core sandwiched between 2 thin transparent , rate controlling ethylene- vinyl acetate copolymer membrane. eg: pilo-20 contains 5mg drug are used. pilo- 40 contains 11mg drug.ii. Implantable silicone rubber device: the constant release rate implantable silicone rubber device for hydrophobic drug like BCNU an intraocular maligancy agent.C) IMPLANTABLE DRUG DELIERY PUMPS:i. Osmotic minipump and implantable infusion system: the osmotic minipump is a useful implanatable drug delvery system with a constant drug delivery rate with a pumping duration of upto 2 weeks. The implantable infusion system , the pumping force is generated by an expending fluid at body temperature. The implantable devices and osmotic minipump, which have developed and used as drug peelet coated with PVA and ethylene vinyl acetate and polysulfone capillary fiber.