bioadhesive and mucoadhesive polymers

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S.K.PATEL COLLEGE OF PHARMACEUTICAL EDUCATION & RESEARCH KHERVA-MEHSANA BIOADHESIVE AND MUCOADHESIVE POLYMERS PRESENTED BY: Nilesh Patel M.Pharm Sem-1 Pharmaceutics GUIDEDED BY: Dr. Girish Patel Assistant Professor Pharmaceutics

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Contents….. Introduction What is Bioadhesive/Mucoadhesive Polymer? Drug Absorption and mechanisms Bio/Micoadhesive Drug Delivery System Bio/mucoadhesive Polymers Types of formulations Targets for bio/mucoadhesive formulations Summary Conclusion

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Adhesion as a process is simply defined as the ‘‘fixing” of two surfaces to eachother. There are many different terminological subsets of adhesion depending upon the environment in which the process occurs. When adhesion occurs in a biological setting it is often termed ‘‘bioadhesion”, furthermore if this adhesion occurs on mucosal membranes it is termed ‘‘mucoadhesion”. Bioadhesion can be defined as the binding of a natural or synthetic polymer to a biological substrate . When this substrate is a mucous layer , term is known as mucoadhesion is often used. Introduction:

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Rationale for bio/mucoadhesion: The API will be released close to the site of action with a consequent enhancement of bioavailability Mucoadhesive drug delivery systems provide a means of enhancing retention at defined sites , if systemic uptake occurs the use of mucoadhesive polymers will not prevent a wider distribution of the API. As a way of achieving site-specific drug delivery through the incorporation of mucoadhesive hydrophilic polymers within pharmaceutical formulations along with the active pharmaceutical ingredient (API).

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What is a bioadhesive polymer?  A polymer is a substance formed by the linkage of a large number of small molecules known as monomers.  A bioadhesive polymer is a synthetic or natural polymer which binds to biological substrates such as mucosal membranes . Such polymers are sometimes referred to as biological ‘glues’ because they are incorporated into drugs to enable the drugs to bind to their target tissues. History: Bioadhesive drug delivery formulations were introduced in 1947 when gum tragacanth was mixed with dental adhesive powder. The aim was to deliver Penicillin into the oral mucosa. This later became Orabase ® , a formulation used to treat mouth ulcers. This product is available as a paste which will stick to the wet surfaces of the mouth and form a protective film over the mouth ulcer. Orabase paste contains polymers such as gelatin, pectin and carboxymethylcellulose.

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Some examples of Orabase products are shown below

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Role of polymers in Bioadhesion : [mechanism] most research has described bioadhesive bond formation as a three step process. Step 1 : Wetting and swelling of polymer Step 2 : Interpenetration between the polymer chains and the mucosal membrane Bioadhesive polymer chains Mucus polymer chains Continue… …

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Step 3 : Formation of chemical bonds between the entangled chains

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Characteristics of Bioadhesive polymers In order for polymers to adhere to mucosal surfaces or epithelial cell they must ideally possess certain characteristics: Flexibility - The flexibility of bioadhesive polymers is important because it controls the extent of the interpenetration between the polymers and mucosal/epithelial surfaces. Hydrophilicity – Polymers that are hydrophilic in nature are able to form strong adhesive bonds with mucosal membranes because the mucus layer contains large amounts of water. Hydrogen bonding – Hydrogen bonding between the entangled polymer chains forms strong adhesive bonds, therefore the presence of hydrogen bond – forming groups such as OH and COOH groups are vital in large quantities. High molecular weig ht – Polymers with a high molecular weight are desirable because they provide more available bonding sites. Surface tensions – Surface tensions are needed to spread the bioadhesive polymer into the mucosal layer epithelial surface.

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Classification of polymers based on their criterias : Criteria Categories Examples Source Semi-natural/natural Synthetic Agarose , chitosan , gelatin Hyaluronic acid Various gums (guar, xanthan , gellan , carragenan , pectin, and sodium alginate). Cellulose derivatives [CMC, thiolated CMC , sodium CMC, HEC, HPC, HPMC, MC, methylhydroxyethylcellulose ]

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Criteria Categories Examples Aqueous solubility Water-soluble Water-insoluble CP, HEC, HPC (waterb38 8C), HPMC (cold water), PAA, sodium CMC, sodium alginate Chitosan (soluble in dilute aqueous acids), EC, PC Continue…..

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Criteria Categories Examples Charges Cationic Anionic Chitosan (soluble in dilute aqueous acids), EC, PC Charge Cationic Aminodextran , chitosan , dimethylaminoethyl (DEAE)- dextran , trimethylated Chitosan Chitosan -EDTA, CP, CMC, pectin, PAA, PC, sodium alginate, sodium CMC, xanthan gum Continue…..

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Criteria Categories Examples Potential bioadhesive forces Non-ionic Covalent Hydrogen bond Electrostatic interaction Hydroxyethyl starch, HPC, poly(ethylene oxide), PVA, PVP, scleroglucan Cyanoacrylate Acrylates [ hydroxylated methacrylate , poly( methacrylic acid)], CP, PC, PVA Chitosan Continue…..

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Some Examples of mucoadhesive polymers: Bioadhesive polymers come from both natural and synthetic sources, some common examples are highlighted below: Acacia gum - This natural polymer is a dried gum obtained from the stem and branches of the tree Acacia senegal . It is used as a thickener in pharmaceuticals. Alginic acid – Is a natural polymer found in the cell walls of brown algae. It is widely used in the manufacture of alginate salts such as sodium alginate which is a constituent of Gaviscon liquid ® . Carbomers – Are polyacrylic acid polymers widely used in the pharmaceutical and cosmetic industries as thickening agents.. Carbomers have a huge advantage in formulation science because they adhere strongly to mucosal membranes without causing irritation, they exhibit low toxicity profiles and are compatible with many drugs. Continue…..

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Hydroxypropyl methylcellulose (HPMC) – This polymer is included in preparations used to moisten contact lenses and in oral gels. Sodium hyaluronate - A high molecular weight biological polymer made of repeating disaccharide units of glucuronic acid and N-acetyl-D - glucosamine. This polymer is used during intraocular surgery to protect the cornea and also acts as a tear substitute in the treatment of dry eyes. Other examples of polymers include: - pectin - polyvinylalcohol (PVA) - polyvinylpyrrolidone (PVP) - tragacanth Continue…..

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Targets for Bioadhesive Formulations: No. Body site Systems Anatomy 1. Eye Mucoadhesive eye drops / inserts/gels 2. Nasal cavity Nasal drug delivery system(nasal drops) 3. Oral cavity Dental gels / buccal systems( gels,tablets,patches,films )

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No. Body site Systems Anatomy 4. Skin Patches, tapes, dressings,films,gel . 5. Vagina Local vaginal delivery systems( tablets,suppositories ) 6. Rectum Local/systemic rectal delivery systems( suppositories,tablets )

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1. The eye Brand Name. Contents Uses Hypotears ® and Sno Tears® Polyvinyl alcohol Lubrication GelTears ® and Viscotears ® Polyvinyl alcohol Lubrication Pilogel ® Pilocarpine , polyacrylic acid Glaucoma Polymers in muco/bioadhesive formulations:

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2. The Nasal Cavity Brand Name. Contents Uses Rhinocort ® Beclomethasone dipropionate , Hydroxypropyl cellulose(HPC) nasal allergy Beconase ® Beclometasone dipropionate carboxymethyl cellulose and microcrystalline cellulose. nasal inflammation and nasal allergies associated with hayfever . Nasacort® Triamcinolone acetonide microcrystalline cellulose nasal inflammation nasal allergy

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3. The oral cavity 3a.The Buccal Mucosa Brand Name. Contents Uses Corlan ® Pellets Hydrocortisone succinate , Acacia mouth ulcers Daktarin ® oral gel Miconazol , pregelatinised potato starch antifungal agent Corsodyl ® Oral gel chlorhexidine gluconate Hydroxypropyl cellulose(HPC) inhibit the formation of plaque

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3b. The sublingual mucosa Brand Name. Active Drug Polymer used Glyceryl Trinitrate (GTN ) aerosol spray and tablet Glyceryl trinitrate , Polyvinyl alcohol ( PVA) Angina pectoris Buccastem ® Is a drug used in the treatment of nausea, vomiting and vertigo. It contains the bioadhesive agents Polyvinylpyrrolidone and Xanthan gum. Suscard ® Is a buccal tablet used in the treatment of angina. It contains the bioadhesive agent Hydroxypropyl methylcellulose (HPMC). Other Examples of Oral products

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How to use mucoadhesive products?

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Buccal tablet GR Patch

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Buccal Film Transdermal patch

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4.The Skin Brand Name Contents Uses Voltarol ® Emulgel Carbomer local relief from pain and inflammation in the tendons, muscles and joints Feldene ® gel Paroxicam , Carbopol 980 hydroxyethyl cellulose. in the treatment of pain, inflammation and stiffness Evorel ® Patch estradiol guar gum polyacrylic acid hormone replacement therapy (HRT)

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5. The Vagina Product Function of Product Bioadhesive Agent Dosage Form Aci-Jel ® Maintains vaginal acidity Acacia, Tragacanth Vaginal Gel Crinone ® Used for Progesterone deficiency Carbomer Vaginal Gel Estring ® Restores Oestrogen deficiency Silicone Polymers Vaginal Ring Gynol-II ® Spermicidal Contraceptive Carboxymethyl cellulose Vaginal Gel Zidoval ® Treatment of bacterial vaginosis Carbomer Vaginal Gel

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Recent advances in mucoadhesive drug delivery system Mucoadhesive microspheres: Microsphere are small spherical particles, with diameters in the micrometer range (typically 1 μm to 1000 μm (1 mm)). have advantages of efficient absorption and enhanced bioavailability of drugs, a much more intimate contact with the mucus layer, and specific targeting of drugs to the absorption site.

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Mucoadhesive microparticles Microparticles are particles between 0.1 and 100 μm in size. Mucoadhesive microparticles is an improved drug delivery system which are believed to bind to the mucus layer coating the stomach and other regions of the GIT. These mucoadhesive microparticles bind to the mucus layer leading either to slow release into the GIT or direct delivery to the gastrointestinal mucosa.

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CONCLUSION : Mucoadhesivepolymers may provide an important tool to improve the bioavailability of the active agent by improving the residence time at the delivery site. The various sites where mucoadhesive polymers have played an important role include buccal cavity, nasal cavity, rectal lumen, vaginal lumen and gastrointestinal tract . Development of novel mucoadhesive delivery systems are being undertaken so as to understand the various mechanism of mucoadhesion and improved permeation of active agents. Many potential mucoadhesive systems are being investigated which may find their way into the market in near future.

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Webster’s Encyclopedic Unabridged Dictionary of the English Language. Thunder Bay Press, Avenel (NJ, USA), 2001. 2. Kaelbe D H and Moacanin J. A surface energy analysis of bioadhesion . Polym ., 18, 1977, pp. 475-481. 3. Gu J M, Robinson J R and Leung S. Binding of acrylic polymers to mucin /epithelial surfaces; Structure-property-relationship. Crit. Rev. Ther . Drug Car. Sys. 5, 1998, pp. 21-67. 4. Duchene D, Touchard F and Peppas N A. Pharmaceutical and medical aspects of Bioadhesive system for drug administration. Drug Dev. Ind. Pharm., 14, 1998, pp. 283-381. 5. Hollingsbee D A and Timmins P. Topical adhesive system, in Bioadhesion Possibilities and Future Trends, Gurny R and Junginger H E Eds., Wissenchaftliche verlag Gesellschaft , Stuttgart, 1990, pp. 140-164. . References :