2007 VJAY POLYMERS.pptx new.pptx 333333333

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INTRODUCTION Significant advances have been made in the development of various drug delivery devices with the help of polymers. They have better physical, chemical& biological properties for efficient therapy .

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DEFINITIoN Polymers are defined as very large macromolecules consisting of repeating units of monomers. The monomers can be linked together to generate a linear polymer. Two types of polymers are there: 1 )Linear Branched polymers 2) Cross linked polymers

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Classification of polymers 1.Based on method of polymerization a) Addition polymers b) Condensation polymers 2. Based on degradability of polymers Biodegradable polymers Non biodegradable polymers Environment responsive polymers

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Homopolymers - consist of chains with identical bonding linkages to each monomer unit. This usually implies that the polymer is made from all identical monomer molecules. These may be represented as : -[A-A-A-A-A-A]- Copolymers - consist of chains with two or more linkages usually implying two or more different types of monomer units. These may be represented as : -[A-B-A-B-A-B]- Classification of Polymers: Polymers are further classified by the reaction mode of polymerization , these include: Addition Polymers - the monomer molecules bond to each other without the loss of any other atoms. Alkene monomers are the biggest groups of polymers in this class. Condensation Polymers - usually two different monomer combine with the loss of a small molecule, usually water. Polyesters and polyamides (nylon) are in this class of polymers. Polyurethane Foam in graphic.

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Classification based upon the physical property related to heating: Thermoplastics - plastics that soften when heated and become firm again when cooled. This is the more popular type of plastic because the heating and cooling may be repeated. Thermosets - plastics that soften when heated and can be molded, but harden permanently. They will decompose when reheated. An example is Bakelite, which is used in toasters, handles for pots and pans, dishes, electrical outlets and billiard balls.

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MUCOADHESIVE POLYMERS: 1) Synthetic polymers a) Cellulose derivatives (methyl cellulose, ethyl cellulose, hydroxyl ethyl cellulose, hydroxyl propyl cellulose, hydroxyl propyl methyl cellulose, sodium corboxy methyl cellulose) b) Poly (acrylic acid) polymers c) Poly (ethylene oxide) d) Poly (vinyl pyrrolidone) e) Poly (vinyl alcohol) 2) Natural polymers: natural polymers obtained from plant and animal origin like Tragacanth, sodium aliginate, karaya gum, guargum, Gelatin, pectin, chitosan

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MUCOADHESIVE POLYMERS USED IN DESIGNING OF DIFFERENT TYPES OF MUCOADHESIVE GASTROINTESTINAL, NASAL, OCULAR, VAGINAL AND RECTAL DRUG DELIVERY SYSTEM Name and form Drug Mucoadhesive polymers Application site Susadrin tablet Nitroglycerin Synchron(modified HPMC) Buccal Buccastem tablet Prochlorzine maleate Xanthan gum , Buccal Salcoat powder spray Beclomethasone dipropionate Hydroxyl propyl cellulose Oral cavity Rhinocort powder Beclomethasone dipropionate Hydroxyl propyl cellulose Nasal

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Pharmaceutical Applications of Polymers for Drug Delivery: TABLET COATING: A) FILM COATING POLYMERS Polymers which are water soluble are used to coat tablets and mask the unpleasant taste those are: • Hydroxyl propyl methyl ( HPMC) • Poly ethylene glycols • Hydroxyl propyl cellulose ( HPC) • Povidone • Sodium carboxy methyl cellulose • Methyl hydroxyl cellulose

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B) ENTERIC COATING POLYMERS: Polymers which are used to give enteric coating to the tablets are: cellulose acetate phthalate Hydroxylpropyl methyl cellulose phthalate, Acryl polymers Poly vinyl acetate phthalate Copolymers of methacrylic acid & its esters ( EUDRAGITS )

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POLYMERIC BINDERS: Binders are added either in dry or liquid form during granulation to form granules or to promote cohesive compacts for directly compressed tablet Acacia, starch tragacanth, gelatin, alginates and cellulose derivatives methyl cellulose, hydroxylpropyl methyl cellulose, poly vinyl pyrrolidone

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POLYMERIC DILUENTS : microcrystalline cellulose (MCC) starch POLYMERIC DISINTIGRANTS: Added to the tablet formulation to facilitate the breakup or disintegration of tablet in contact with the water in gastro intestinal tract. Also added to hard gelatin shell to promote the moisture penetration. Starch, cellulose Sodium starch glycolate –NF Cross-linked polyvinyl pyrrolidine -NF Carboxy methyl starch

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PLASTICIZERS: Polymers which are used as plasticizers include: Polyethylene glycol 200-400 Polysorbates (tweens) Sorbitan esters POLYMERS USED IN SUSPENSIONS: I) Deflocculated suspensions In deflocculated suspensions we add polymers which exhibit thixotropic behavior I.e., gel-sol-gel transformation Such a behavior improves the physical stability of suspensions. Methyl cellulose, hydroxyl propy methyl cellulose, sodium carboxy methyl cellulose, Poly acrylic acid (carbapols).

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2) Flocculated suspensions: Some polymers acts as a flocculating agents Example: xanthan gum used in sulfa guanidine suspension

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POLYMERS USED IN IMPROVING AQUEOUS SOLUBILITY OF POORLY SOLUBLE DRUGS: I) Cyclodextrins inclusion complex formation ii) Polymeric micellular solubilization technique iii) Polymer-drug conjugation 1) Cyclodextrins inclusion complex formation: The solubility of a drug in an aqueous solution can be increased by adding cyclodextrin (CD) in the solution. CD is a cyclic oligosaccharide consisting of six, seven, or eight β-D-glucopyranose residues in (β-1, 4) linkages, called α-, β-, or γ-, respectively. It forms a rigid, truncated cone (torus)–shaped molecule with a hollow interior of the torus. The hydroxyl groups of the molecule face to the exterior of the torus, and the skeletal carbons and ether linkages of the glucopyranose are oriented to the interior of the central cavity.

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When a drug molecule is of the appropriate size and the CD is in an aqueous solution, the nonpolar segment of the drug enters the nonpolar interior portion (hydrophobic cavity) of the CD. This inclusion complexation separates the nopolar portion of the drug from the aqueous, polar environment so that the solubility of the drug is further increased. Beta-CD shows the parenteral toxicity. The two modified β-CDs which do not show parenteral toxicity are the Hydroxypropyl-β-cyclodextrins (HP-β-CDs) and sulfobutylether-β-cyclodextrins (SBE-β-CDs). Example: - inclusion complexation of ZIPRARIDONE MESYLATE (anti-psychotic drug) with (SBECD’S)

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CD inclusion has been shown to improve bioavailability of compounds administered by other routes including ocular, topical, nasal, and rectal routes. Some important applications particularly applicable for insoluble compounds are summarized below. 1. Solid preparations Oral bioavailability of poor water-soluble drugs can be improved. Physical stability of compounds in their metastable forms can be enhanced by the inhibition or prevention of crystal growth. Shelf life of drugs can be extended by increasing their stability. 2. Liquid preparations Solubility and stability of the drug in water can be improved. 3. Suspensions and emulsions Caking, creaming, and phase transitions can be suppressed by the protective sheath of CDs. Physical stability of the dispersed system can be improved. 4. Semisolid preparations Topical bioavailability can be improved by the enhanced release of a drug from ointment or suppository bases. Waterabsorbing capacity of oleaginous and water in oil bases can be improved by hydrophilic CDs.

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Polymeric micellular solubilization: Use of polymeric micelles has been found to be effective in delivering hydrophobic molecules. When amphiphilic block co-polymers (i.e. having hydrophilic and hydrophobic segments) are placed in an aqueous environment, the large solubility difference between the hydrophilic and hydrophobic segments drives the formation of polymeric micelles. The hydrophobic segments form an inner core, where hydrophobic drugs can be loaded, while the hydrophilic segments surround the core to stabilize and increase the solubility of the drug.

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Polymeric micelles represent a separate class of micelles and are formed from copolymers consisting of both hydrophilic and hydrophobic monomer units. Some Examples of Copolymers Used to Prepare Drug-Loaded Micelles Pluronics Poly caprolactone- b- PEG Poly ( N -isopropylacrylamide)- b -PEG Poly (aspartic acid)- b -PEG Poly (ethylene oxide)- b -poly (styrene) Poly (ethylene oxide)-b-poly (propylene oxide)- b- poly(ethylene oxide) PEG-PE

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Polymer-drug conjugation: Polymer drug conjugate is composed of a drug that is covalently bound to a polymer, which may be either hydrophilic or hydrophobic. The linkage of a drug to a macromolecular carrier will alter its pharmacokinetics properties of drug, enhances the bioavailability, specificity and duration of action. Applications : 1) Increases the solubility of poorly soluble drugs Example: cisplatin conjugated with dextran

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Improves tumor targeting and reduces the toxicity of drugs Drug Polymer conjugate Advantage 5-fluorourasil Chitin Reduced toxicity Doxorubicin Poly(Hydroxyl metha propyl A crylate) ( HMPA) conjugated Reduced toxicity,tumour specific targeting,increased aqueous solubility Paclitaxel HPMA Reduced toxicity, increased tumor uptake

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3) Enhances the stability and biological half-life of protein/peptide drugs. Examples: Streptokinase conjugated to dextran sold under the name streptidikase was one of first therapeutic enzyme approved for the treatment of thrombosis . PEG- asparaginase used for the treatment of lymphocytic leukemia. Hemoglobin has been conjugated to PEG and this PEG-HB conjugate is undergoing phase-II clinical trial for use for blood transfusion.

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POLYMERS IN DISPERSE SYSTEMS: Polymers are used in suspensions. Emulsions. And other dispersions. Primarily to minimize or control sedimentation. The rheological character given to disperse s stems also plays a role in maintaining pharmaceutical preparations at their application site. For example: Highly fluid skin lotions may run. Whereas viscous preparations tend to remain In addition to their effect on dispersion rheology. Polymers may also play a roleactivity. Some polymers can directly improve emulsion stability; the ability of acacia to Function as an emulsifier is well known.

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Eudragits : Composition of the Poly methaacrylic acid (PMA) polymer is -30% and they form aqueous polymeric dispersion suspension and emulsions. Eudragit L 30D Eudora NE 30D Eudragit RL 30D Eudragit RS 30D AQUACOAT – ethyl cellulose SURELEASE E - 7050 - contains ethyl cellulose and dibuty sebecate as a plasticizer SURELEASE E - 19010 - contains ethyl cellulose and fractionated oil as a plasticizer

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Polymeric excipients Trade name Manufacturer Applications Carbomer 934,934P,and 940 Carbapol 934,934P and 940 BF Goodrich Co... Emulsifier, suspending agent, suspension stabilizer, viscosity enhancer Carbomer 1342 pemulen BF Goodrich Co... suspension stabilizer, Emulsifier, thickening agent Carboxymethylcelulose sodium Natrosol, Blanose Hercules,inc stabilizer, suspending agent, thickening agent carrageenan Genu carrageenan stamere Hercules,inc Meer corp.… suspension stabilizer, Emulsifier, thickening agent crospovidone polyplasdone ISP technologies inc… Clarifying agent suspension stabilizer Ethyl cellulose Ethyl cellulose Ethocel Hercules,inc Dow chemical co… Coacervation( U.S patent 3,567,650, microencapsulation Guar gum Supercol Guar gum merezan Aqualon co… Meer corp.… thickening agent, suspension stabilizer

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Polaxomer Pluronic Lutrol BASF corp. BASF PLC Emulsifier, dispersant, wetting agent, gel forming agent Poly carbophil Noveon B.F. Goorish co. thickening agent, emulsion stabilizer Poly ethylene glycol Carbowax Lutrol Hodag B.F. Goorish co. Emulsifier .emulsion stabilizer, solubilizer, Suspending agent, Poly glycerol esters of fatty acids Caprol Hodag Abitec.corp Calgene inc… Emulsifier ,stabilizer Polyoxyl 35 castor oil Cremophor EL BASF corp. Emulsifier, stabilizer wetting agent Polyoxyl 40 hydrogenated castor oil Cremophor RH 40 BASF corp. Emulsifier, solubilizer, wetting agent Poly vinyl alcohol Airvol Elvanol Air products DuPont Ophthalmic lubricant, thickening agent Povidone Plasdone Kollidone ISP Technologies inc… BASF corp. Binder , thickening agent Suspension stabilizer,complexing aid

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HYDROGELS: Hydrogels are three- dimensional, hydrophilic polymeric network capable of imbibing large amount of water but in which they are insoluble. High water content of these materials improves their biocompatibility. Hydrogel based drug delivery systems have been used for oral, rectal, ocular and subcutaneous applications. Hydrogels undergo reversible sol-gel phase transition in response to physiological (temperature, pH, presence of ions, blood glucose levels) or other external (electric current, light) stimuli.

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PH-sensitive hydrogels: Hydrogel can undergo swelling due to a change in the pH of the environment, resulting in easier diffusion of drug molecules through the expanded polymer network. Polymers like: - polyacrylamide, polyacrylicacid, poly (meth acrylic acid), poly (diethylaminoethyl methacrylate) and poly (dimethylamino ethyl methacrylate) are used in p H sensitive polymer.

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PH-sensitive hydrogels have a potential use in site-specific delivery of drugs to specific region of GI tract.

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THERMOSENSITIVE HYDROGELS: Poly (ethylene oxide)-b-poly (propylene oxide)-b- Poly (ethylene oxide) called as ploxomers, commercially available as pluronics. This type of hydrogel is most commonly used in ocular drug delivery. Poly (ethylene glycol)-poly (lactic acid- coglycolic acid) - Poly (ethylene glycol) [PEG-PLGA-PEG] used in sustained injectable drug delivery system. GLUCOSE SENSITIVE HYDROGEL SYSTEM. Various glucose-sensitive hydrogels have been developed as self-regulated insulin delivery systems. The most common method involves adding glucose oxidase to pH-sensitive hydrogels..As glucose molecules go into the membrane, they are converted into gluconic acid by glucose oxidase, resulting in decrease of pH in the hydrogel. This causes swelling of the membrane, and insulin can be released to the surroundings through the swollen membrane. Example of glucose sensitive hydrogel is poly (N, N-dimethylaminoethyl methacrylate-co- ethacrylamide) Membrane contains poly (N, N-dimethylaminoethyl methacrylate-co-ethacrylamide )

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RESERVIOR SYSTEMS: In these systems the drug containing core is surrounded by a water insoluble polymeric membrane. Examples of polymers that are commonly used are ethyl cellulose , poly (Ethyl vinyl acetate ) and various acrylate copolymers . There are several drug delivery systems that are designed to provide reservoir controlled drug release. Examples Ocusert,Progestasert,Reservoir designed transdermal patches.

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MATRIX SYSTEMS: In matrix designed drug delivery systems, the drug is homogeneously dispersed, either at the molecular level or as solid particle, with in a polymeric medium. Examples polymers used in matrix system are Hydroxyl propyl methyl cellulose, Carboxy Methyl Cellulose, Xanthan gum

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OSMOTICALLY CONTROLLED DRUG DELIVERY SYSTEM: These devices are designed to have a semi-permeable membrane that allows water to move in, but prevents drug molecules from moving out. The drug molecules exit through a small opening due to the increase in pressure. Polymers commonly used in these systems are cellulose diacetate , cellulose triacetate , cellulose acetate butyrate, ethyl cellulose, and Eudragits.

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POLYMERS IN NANOPARTICLES Nano particles are the type of colloidal drug delivery system where particle size ranges from 10-100 nm in diameter. Nano particles made of non-biodegradable and biodegradable polymers. Polymers used for the preparation of nanoparticles are Albumin, gelatin, alginate, chitosan, dextrane Poly (alkyl cynoacrylates), Poly (lactic acid), poly (glycolic acid) and poly (lactic-co-glycolic acid). APPLICATIONS OF NANOPARTICLES CONTAING POLYMERS: Poly (lactic acid) (PLA) and poly (lactide-co-glycolic acid) (PLGA): Are also used as nanoparticles for parenteral administration.

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APPLICATION MATERIAL PURPOSE Cancer therapy targeting poly (alkyl cynoacrylate)NPs Anticancer agents targeting, reduced toxicity, enhanced uptake of anticancer agents Intracellular targeting poly (alkyl cynoacrylate)NPs with antiviral agents targeting reticular endothelial intracellular infections ocular delivery Poly(alkyl cynoacrylate)NPs with steroids, anti-inflammatory agents Improve the retention of the drug Preoral absorption Poly ( methaacrylate)NPs with proteinS Enhanced bioavailability ,protection from GIT enzymes Other applications Poly(alkyl cynoacrylate)NPs with peptides Cross BBB Other applications Poly(alkyl cynoacrylate)NPs Improve the absorption and permeation for transdermal application

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Indian journal of p harmaceutical education and research,jan-mar 2006,nano particle:a novel collidal drug delivery system. Indian journal of pharmaceutical education and research,jan-mar 2006,An overview of polymers used in development ofv drug delivery. Biodegradable polymers: which, when,why?, Indian jiournal of pharmaceutical science, september-october 2007,page:616-624 Muco adhesive polymers:mean of improving drug delivery,pharma times volume 38 april 2006,page no:25-28 Smart hydrogels in controlled drug delivery,pharma times, volume 38,nov2006,page no 13-18