Polymers

Polymer is a heart of controlled drug delivery system. Application of polymers are increasing in pharmaceuticals these days .

1. POLYMERS In Pharmaceuticals Presented by: Pranali .M Palandurkar University department of pharmaceutical Sciences R.T.M.N.U Nagpur

2. Contents Introduction Classification Properties Advantages Applications

3. “ Polymer are long chain organic molecules assembled form many smaller molecules called as monomer connected by covalent bonds or chemical bonds ” Polymers are macromolecules having very large chains contain a variety of functional groups, can be blended with other low and high molecular weight material A polymer with two different monomers is known as a copolymer or homopolymer Their use for biomedical and pharmaceutical applications has gained an enormous impact during the past decades. The pharmaceutical applications of polymers range from their use as binders in tablets to viscosity and flow controlling agents in liquids, suspensions, and emulsion. Polymers can be used as film coatings to disguise the unpleasant taste of a drug, to enhance drug stability, and to modify drug release characteristics . INTRODUCTION

4. The reaction involving combination of two or more monomer units to form a long chain polymer is termed as polymerization By changing the molecular weight, the physical and mechanical properties of the polymer can be tailor-made. This can be achieved by changing the structure of the monomer building blocks or by blending them with other polymers .

5. Classification of polymers Natural polymer Natural polymers are the substances which are obtained by natural sources like plant and animal sources. The specific application of plant derived polymer in pharmaceutical formulations include their use in the manufacture of solid monolithic matrix systems, implants, etc Examples- Proteins-collagen, keratin, albumin. Synthetic polymer Synthetic polymers are industrially produced chemical substances consisting of a number of molecules linked together with covalent bond. A wide variety of synthetic polymers are available with variation in main chain as well as side chain. Exanple - polyester , polyanhydrides , polyamides, polyglycolic acid A) Based on origin Semi Synthetic Synthetic polymers are polymers obtained by making modification in natural polymers artificially in a lab. These polymers formed by chemical reaction   and are of commercial importance Example-cellulose derivative (rayon)

6. B) Based on Bio-stability

7. C) Based on structure

8. Elastomers : Elastomers are rubber-like solid polymers, that are elastic in nature i.e stretched by applying a little force. Example - N eoprene  rubber, buna -s and buna -n  Thermoplastic polymers   :Polymers which contain intermolecular forces higher than Elastomers but less than Fibers. They are usually linear chain polymers and can be remolded again. Examples: Polythene, Polyvinyl Chlorides, etc. Thermosetting plastics  : Polymer which are having highly branched chain molecules with extensive cross linking and if heated becomes infusible and cannot be reused. Example: melamine, Bakelite etc. Fibres: P olymers which are a thread like in nature, and can easily be woven. They have strong inter-molecules forces between the chains giving them less elasticity and high tensile strength. The intermolecular forces may be hydrogen bonds or dipole-dipole interaction. Fibres have sharp and high melting points. Example: Nylon-66. D)Based on M olecular Force

9. E)Based on Mode of  Polymerization

10. Properties A) Crystalline and amorphous polymers: Amorphous or glassy polymers do not generally display a sharp melting point; instead, they soften over a wide temperature range. Polymer strength and stiffness increases with crystallinity as a result of increased intermolecular interactions. From a pharmaceutical prospective, good barrier properties are needed when polymers are used as a packaging material or as a coating. Crystallinity increases the barrier properties of the polymer. On the other hand, a less crystalline, or an amorphous polymer is preferred when the release of a drug or an active material is intended.

11. B) Thermal transitions Thermal transitions in polymers can occur in different orders. That is, the volume of a polymer can change with temperature as a first-or second-order transition. When a crystal melts , the polymer volume increases significantly as the solid turns to a liquid. The melting temperature (Tm) represents a first-order thermal transition in polymers. On the other hand, the volume of an amorphous polymer gradually changes over a wide temperature range or so-called glass transition temperature. This behaviour represents a second-order thermal transition in polymers .

12. C) Plasticized polymer A plasticizer is added to a polymer formulation to enhance its flexibility and to help its processing. It facilitates relative movement of polymer chains against each other. This results in a reduction in the glass transition temperature of the mixture. Since plasticizers increase molecular motion, drug molecules can diffuse through the plasticized polymer matrix at a higher rate depending on the plasticizer concentration D) Molecular weight There are different ways that molecular weights of a polymer can be expressed: by the number of the chains, by the weight of the chains (the chain size), or by viscosity. However, the two most common ways are number ( Mn ) and weight (Mw) average calculations. Based on that polymers can be termed as polydispered and monodispersed .

13. E) Mechanical properties Depending on their structure, molecular weight, and intermolecular forces, polymers resist differently when they are stressed. They can resist against stretching,compression , bending and dynamic loading. With increasing molecular weight the level of intermolecular forces, polymers display superior properties under an applied stress F) Viscoelastic Properties Materials that exhibit both viscous and elastic characteristics when deformed under stress are known to be viscoelastic . Polymers are neither a pure elastic nor a pure fluid material. They have the ability to store energy (display elastic behaviour ) and to dissipate it (display viscous behaviour ). For this reason, most polymers are viscoelastic materials.

14. Advantages T he polymer enhances the pharmacodynamic and pharmacokinetic properties of biopharmaceuticals though several sources, such as, increases the plasma ½ life, decreases the immunogenicity, boost stability of biopharmaceuticals, Polymer can also improves solubility of low molecular weight drugs, and has potential for targeted drug delivery Sustained delivery of drug can be achieved by polymers hence decrease in dosing frequency. Polymer can be use for taste masking of bitter drug which increases the patient compliance . Localised delivery of drug- The product can be implanted directly at the site where drug action is needed Due to biodegradable polymers their degradability reduces the need for subsequent surgical removal, saving time and money The polymer can protect the drug from the physiological environment and hence improve its stability in vivo

15. Application of polymer in Fomulation of control drug delivery system Controlled drug delivery occurs when a polymer ,whether natural or synthetic, is judiciously combined with a drug or other active agents such away that the active agent is released from the material in a predesigned manner . 1.Extended release dosage forms : Extended and sustained release dosage forms prolong the time that’ systemic drug levels are within the therapeutic range and thus reduce the number of doses the patient must take to maintain a therapeutic effect there by increasing compliance. The most commonly used water insoluble polymers for extended release applications are the ammonium ethacrylate copolymers cellulose derivatives ethyl cellulose and cellulose acetate, and polyvinyl derivative, polyvinyl acetate

16. 2.Gastro retentive Dosage forms : To achieve gastro retention mucoadhesive and low density, polymers have been evaluated, with little success so far their ability to extend gastric residence time by bonding to the mucus lining of the stomach and floating on top of the gastric contents respectively.

17. 3.Ocular drug delivery system –It allows prolonged contact with corneal surface of eye . Example – P illocarpine in the treatment of glaucoma –In this mucoadhesive polymers ( Polyacrylic acid or copolymer of acetate vinyl &ethyl) are used as barrier to control the drug release. The efficiency of ocular drug delivery is improved through the use of polymeric implants i.e Occusert that are implanted under the cul-de-sac of the eye.

18. 4.Trandermal drug delivery –It involves the diffusion of the drug through the skin and ultimately absorption into the systemic circulation. The drug delivery system is composed of several layers, namely a metallic backing layer ,which is impermeable to drug diffusion ,the drug containing reservoir, a rate controlling membrane and an adhesive layer. In the matrix drug is dissolved or dispersed with solid polymer(acrylate co –polymer)

19. 5.Polymers in nanoparticles Nanoparticles have size range of 10-1000nm. In nanoparticle drug delivary system drug is attached, entrapped and dissolve to polymeric matrix. Example of synthetic biodegradable polymers are poly lactide , poly( lactide -co- glyolide ), poly-ɛ- caprolactone and polyanhydrides .