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Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D

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By : Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D KLE University s College of Pharmacy BELGAUM 590010, Karnataka, India Cell No: 00919742431000 – PowerPoint PPT presentation

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Title: Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D


1
POLYMER SCIENCE
  • By
  • Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D
  • KLE Universitys College of Pharmacy
  • BELGAUM 590010, Karnataka, India
  • Cell No 00919742431000
  • E-mail bknanjwade_at_yahoo.co.in

2
CONTENTS
  • Introduction
  • Classification of Polymers
  • Applications in Conventional Dosage Forms
  • Applications in Controlled Drug Delivery
  • Biodegradable Polymers
  • Natural Polymers
  • References

3
INTRODUCTION
  • Polymers are used extensively in our daily
    routine life.
  • In pharmaceutical preparations also they have
    several applications
  • e.g. In mfg of bottles, syringes, vials,
    cathaters, and also in drug formulations.

4
What is Polymer?
  • Polymer word is derived from Greek roots Poly
    meaning many and Meros meaning parts.
  • Definition
  • Polymers are long chain organic
    molecules assembled from many smaller molecules
    called as monomers.

5
  • Copolymer
  • Polymers formed from two or more
    different monomers are called as copolymers.
  • - A B A B A B
  • Homopolymer
  • Polymers formed from bonding of
    identical monomers are called as homopolymers.
  • - A A A A A -

6
CLASSIFICATION
  • A. Based on origin
  • a) Natural Polymers
  • e.g. Proteins Collagen, Keratin, Albumin
  • Carbohydrates starch, cellulose,
    glycogen.
  • DNA, RNA
  • Synthetic Polymers
  • e.g. polyesters, polyanhydrides, polyamides.
  • B. Based on Bio-stability
  • a) Bio-degradable Polymers
  • e.g. polyesters, proteins, carbohydrates, etc
  • b) Non biodegradable Polymers
  • e.g. ethyl cellulose, HPMC, acrylic polymers,
    silicones.

7
  • C. Based on Reaction mode of
    Polymerization
  • a) Addition Polymers
  • Here, the monomer molecules bond to
    each other without the loss of any other
    atoms.
  • e.g. Alkene monomers
  • b) Condensation Polymers
  • Usually two different monomers
    combine with the loss of small molecule,
    usually water.
  • e.g. polyesters, polyamides.

8
  • D. Based on Interaction with Water
  • a) Non biodegradable Hydrophobic
    Polymers
  • These are inert compounds and are
    eliminated intact from the site of application.
  • e.g. polyethylene vinyl acetate, polyvinyl
    chloride.
  • b) Hydrogels
  • They swell but do not dissolve when
    brought in contact with water.
  • e.g. polyvinyl pyrrolidone
  • c) Soluble Polymers
  • These are moderate mol. wt
    uncross-linked polymers that dissolve in water.
  • e.g. HPMC, PEG
  • d) Biodegradable Polymers
  • These slowly disappear from the
    site of administration in response to a chemical
    reaction such as hydrolysis.
  • e.g. Polyacrylic acid. Polyglycolic acid.

9
CHARACTERISTICS OF IDEAL POLYMER
  • Should be inert and compatible with the
    environment.
  • Should be non-toxic.
  • Should be easily administered.
  • Should be easy and inexpensive to fabricate.
  • Should have good mechanical strength.

10
Criteria Followed In Polymer Selection
  • It must be soluble and easy to synthesize must
    have a finite molecular wt.
  • Should provide drug attachment and release sites
    for drug polymer linkages.
  • Should be compatible with biological environment,
    i.e. non-toxic and non-antigenic.
  • Should be biodegradable or be eliminated from
    body after its function is over.

11
Applications in Conventional Dosage Forms
  • Tablets
  • - As binders
  • - To mask unpleasant taste
  • - For enteric coated tablets
  • Liquids
  • - Viscosity enhancers
  • - For controlling the flow
  • Semisolids
  • - In the gel preparation
  • - In ointments
  • In transdermal Patches

12
Applications In Controlled Drug Delivery
  • Reservoir Systems
  • - Ocusert System
  • - Progestasert System
  • - Reservoir Designed Transdermal Patches
  • Matrix Systems
  • Swelling Controlled Release Systems
  • Biodegradable Systems
  • Osmotically controlled Drug Delivery

13
  • A. Reservoir System
  • Ocusert System
  • - Novel means of controlled ocular drug
    delivery
  • - Used for max 7 days treatment of Glaucoma
  • - Consists of core reservoir of pilocarpine
    alginic acid sandwiched between two sheets of
    transparent, lipophillic, rate controlling
    membrane of ethylene-vinyl acetate copolymer.
  • - Inserted in cul-de-sac, lachrymal fluid
    enters the system and the dissolved drug slowly
    gets released through polymeric membrane.

14
  • Progestasert system
  • - Used for once-a-year contraception
  • - Consists of drug saturated liquid medium
    encapsulated in a polymeric membrane.
  • - Progesterone is released at a constant
    rate of 65 µg/day.
  • - Polymers used are
  • Silicone elastomers, polyethylene,
    ethylene-vinyl acetate.

15
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16
  • Transdermal Patches
  • - Drug is sandwiched between drug
    impermeable backing and drug permeable rate
    controlling polymer.
  • e.g. Ethylene-vinyl acetate copolymer
  • - In the reservoir, drug is dispersed in
    solid polymer matrix.
  • e.g. Polyisobutylene
  • - On the external surface, there should be
    adhesive polymer.
  • e.g. Silicone Polymer, Polyacrylates.

17
Transdermal Controlled Drug Delivery
Transdermal Controlled Drug Delivery
18
B. Osmotically Controlled Drug Delivery System
  • Drug is coated with semi-permeable polymer
  • e.g. Cellulose acetate.
  • Water generates osmotic pressure gradient by
    permeating through semi-permeable membrane.
  • Due to that drug pumps out of delivery orifice
    over a prolonged time at a defined rate.

19
C. Biodegradable System
  • Mainly used for parenteral controlled drug
    delivery.
  • Drug is encapsulated in biodegradable
    microcapsules which are suspended in aqueous /
    oleaginous medium and injected subcutaneously or
    intra-muscularly.
  • Polymers used for microcapsules are
  • Gelatin, dextran, polylactate, lactide
    glycolide copolymer.
  • The release of drug is controlled by the rate of
    bio-degradation of polymer.

20
D. Matrix Systems
  • Drug particles are enclosed in a matrix
    environment formed by cross-linking of polymer
    chains.
  • For the drug to get released, it has to be first
    dissolved in surrounding polymer and then diffuse
    through the polymer structure.
  • Polymers used are
  • polyalkyls, polyvinyls, etc.
  • Example Nitroglycerine releasing system for
    prophylaxis or treatment of angina pectoris.

21
E. Swelling Controlled Release Systems
  • Drug is enclosed in a collapsible drug
    compartment inside a rigid, shape-retaining
    housing.
  • The shape between external housing and drug
    compartment contains laminate of swellable,
    hydrophillic cross-linked polymer.
  • e.g. polyhydroxyalkyl methacrylate.
  • This polymer absorbs GI fluid through annular
    openings in the bottom of housing.

22
Because of this, laminate swells and
generates hydrodynamic pressure and
induces the delivery of drug formulation through
the orifice.
  • Drug delivery orifice
  • Shape retaining housing
  • Collapsible drug container
  • Swellable polymer
  • Liquid drug formulation
  • Annular openings

23
Biodegradable Polymers
  • Definition
  • Biodegradable polymers are defined as polymers
    comprised of monomers linked to one another
    through functional groups and have unstable
    links in the backbone.
  • They slowly disappear from the site of
    administration in response to a chemical reaction
    such as hydrolysis.

24
Classification
  • Synthetic Polymers
  • a) Aliphatic polymers
  • b) Polyphospho-esters
  • c) Polyanhydrides
  • d) Polyorthoesters
  • Natural Polymers
  • a) Collagen
  • b) Albumin
  • c) Casein
  • d) gelatin
  • Environment Responsive Polymers
  • a) Thermo sensitive Poly acryl amide
  • b) pH sensitive Methyl vinyl ether

25
Mechanism of Biodegradation
  • A. Hydrolytic Degradation
  • Breakdown of polymer by water by cleaving
    long chain into monomeric acids. This is done by
    two ways
  • Bulk eroding polymers
  • e.g. Polylactic acid (PLA)
  • Polyglycolic acid (PGA)

26
  • Surface Eroding Polymers
  • e.g. Polyanhydrides
  • B. Enzymatic Degradation
  • Exact mechanism is not known but may be due to
    lysis of long polymer chain by attaching to it.

27
  • Factors affecting Biodegradation
  • - Polymer morphology
  • - pH ionic strength
  • - Drug polymer interaction
  • - Chemical composition and structure
  • Applications
  • - Sutures used during the surgery
  • - For orthopaedic applications
  • - For tissue regeneration
  • - For protein drug delivery

28
A NEW BIODEGRADABLE POLYMER POLYKETAL
  • Advantages over existing biodegradable polymers
  • Is biodegradable in FDA approved compounds.
  • Synthesis is easy
  • Degradation does not produce inflammation caused
    by acid produced.
  • Quick degradation (within a week)
  • Applications
  • 1. Delivery of anti oxidants in acute liver
    failure
  • 2. In any protein based vaccine.

29
Natural Polymers
  • Natural polymers remains the primary choice of
    formulator because
  • - They are natural products of living organism
  • - Readily available
  • - Relatively inexpensive
  • - Capable of chemical modification
  • Moreover, it satisfies most of the ideal
    requirements of polymers.
  • But the only and major difficulty is the batch-
    to-batch reproducibility and purity of the sample.

30
  • Examples
  • 1) Proteins
  • - Collagen Found from animal tissue.
  • Used in absorbable sutures, sponge wound
    dressing, as drug delivery vehicles
  • - Albumin Obtained by fabrication of blood
    from healthy donor.
  • Used as carriers in nanocapsules
    microspheres
  • - Gelatin A natural water soluble polymer
  • Used in capsule shells and also as coating
    material in microencapsulation.

31
  • 2) Polysaccharides
  • - Starch
  • Usually derivatised by introducing acrylic
    groups before manufactured into microspheres.
  • Also used as binders.
  • - Cellulose
  • Naturally occuring linear polysaccharide. It
    is insoluble in water but solubility can be
    obtained by substituting -OH group.
  • Na-CMC is used as thickner, suspending agent,
    and film formers.
  • 3) DNA RNA
  • They are the structural unit of our body. DNA
    is the blueprint that determines everything of
    our body.

32
  • Polysaccharide hydrogels for modified release
    formulations.
  • Hydrogels are three-dimensional, hydrophilic,
    polymeric networks, with chemical or physical
    cross-links, capable of imbibing large amounts of
    water or biological fluids.
  • Among the numerous macromolecules that can be
    used for hydrogel formation, polysaccharides are
    extremely advantageous compared to synthetic
    polymers

33
  • Biodegradable dextran hydrogels for protein
    delivery applications
  • Hydrogels offer good opportunities as protein
    drug delivery due to its inherent
    biocompatibility.
  • It guarantees safe and controlled delivery of
    proteinacious drugs.
  • Dextran is a natural polysaccharide and offers
    good properties to be used in hydrogel system.
  • Here, special attention is given to network
    properties, protein delivery, degradation
    behavior and biocompatibility.

34
MucoAdhesive Polymers
  • These polymers have carried major attention
    recently for the role they may play in following
    features of controlled drug delivery
  • Prolonged residence time at absorption site.
  • e.g. by controlling GI transit,
  • for transnasal drug delivery.
  • Localization of drug in specified regions to
    improve the bioavailability.
  • e.g. targetting to the colon.
  • Examples Polyacrylates, Chitosans, Polyglucan
    derivatives.

35
REFERENCES
  • Novel drug delivery systems Y.W.Chien Dekker
    50
  • Eastern Pharmacist April, 2001.
  • August, 1998
  • Bioadhesive drug delivery system
  • Dekker 98
  • Encyclopedia of controlled drug delivery systems.

36
THANK YOU
Cell No 00919742431000 E-mail
bknanjwade_at_yahoo.co.in
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