Describing the properties of polymers used in the pharmaceuticals

1. POLYMERS in PHARMACEUTICALS
By
Clinton Chayan Dhar
PhD Researcher,
School Of Chemical Engineering,
Yeungnam University,
Republic of South Korea.
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2. Polymer Science
• Polymer Science or Macromolecular Science is a
subfield of materials Science concerned with
polymers, Primarily synthetic polymers such as
plastics and elastomers.
• Polymer Science has been the backbone for the
development of new formulations for past few
years and its advances have led to development
of several applications in pharmaceutical
science.
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3. Polymer Science cont.
Other definitions-
A Polymer is like a thread that is joined by many coins
punched through the center, in the end we get a
string of coins, the coins would be the monomers
and the chain with the coins would be the polymer.
E.g. Polyethylene = Ethylene-ethylene-
ethylene-ethylene.
Polymers are long chain giant organic molecules
assembled from many smaller molecules called
monomers. A polymer is analogous to a necklace
made from many small beads.
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4. At a Glance
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5. Chemical nature of some common
polymers
1. Polyethylene (LDPE) (Addition polymer)
Formula- -(CH2-CH2)n-
Monomer- Ethylene (CH2=CH2)
Properties- Soft, Waxy Solid
Uses- Film Warp, Plastic bags etc.
2. Butyl Rubber (Copolymer)
Monomer A- H2C=C(CH3)2
Monomer B- H2C=C-CH-CH2
Properties- Elastic Strong rubber material.
Uses- Inner tubes of tires.
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6. Chemical nature of some common
polymers
3.Polyvinyl Chloride (PVC) (Addition Polymer)
Formula : -(CH2-CHCL)n-
Monomer : Vinyl Chloride (CH2=CHCL)
Properties : Strong rigid Solid
Uses : Pipes, Siding, Flooring.
4.Polypropylene (Diff Grades) (Addition Polymer)
Formula : -[CH2-CH(CH3)]n-
Monomer : Propylene (CH2=CHCH3)
Properties : Atactic, Soft, Elastic solid
Uses : Similar to LDPE carpet, upholstery etc.
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7. Some important Polymers used for
drug delivery
• Hydroxyl propyl Methyl Cellulose
It is a semisynthetic, Inert, Viscoelastic polymer used as an
ophthalmic lubricant as well as an excipient and controlled
delivery component in oral medicaments. It is also found
in variety of commercial products.
Description- It is solid and slightly off-white to beige
powder in appearance and may be formed in granules.
Category- Suspending Agent, Viscosity enhancer, Tablet
binder, Coating agent, Film forming agent, Emulsion
stabilizer etc.
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8. Some important Polymers used for
drug delivery
• Micro crystalline cellulose (MCC)
MCC is a unique ingredient. In water with shear it forms
three dimensional matrix comprised of invisible
microcrystals that form an extremely stable, thixotropic
gel. It functions at any temp and provides superior freeze
and heat stability to finished products.
Category- Tablet and capsule diluent, Tablet disintegrate,
Suspending agent, Viscosity enhancer etc.
Description- Purified, Partially depolymerized cellulose
occurs as a white odorless crystalline powder composed of
porous particles. Available in diff particle size grades and
prop.
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9. Some important Polymers used for
drug delivery
• Guar gum-
Guar gum is a natural polymer obtained from ground
endosperm of guar beans.
Category- Tablet binder, suspending and viscosity
increasing agent, Tablet disintegrating agent etc.
Chemistry- Chemically gaur gum consist of
polysaccharides composed of sugars galactose and
mannose.
Description- White to yellowish-white powder.
Odorless and bland in taste.
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10. Some important Polymers used for
drug delivery
• Polyethylene Glycol (PEG)-
Polyethylene glycol is a polyether compound with many
applications from industrial manufacturing to medicine.
Category- Suppository base, Solvent, Tablet and capsule
lubricant, Ointment base etc.
Diff grades of PEG:
PEG200,300,400,600,800,1000,1500,1540,2000,3000,
4000,6000,8000, 20,000, 35,000.
Description- Clear, Colorless or Slightly Yellowish,
Viscous liq.
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11. CHARACTERISTICS OF IDEAL
POLYMER SYSTEM
• Inert and compatible with environment.
• Nontoxic.
• Easily administrable.
• Easy and inexpensive to fabricate the dosage
form.
• Good mechanical strength.
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12. CLASSIFICATION OF POLYMERS
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13. Bio- degradable polymers
1. Natural bio-degradable polymers- These
polymers are very common in nature. Natural
biodegradable polymers like collagen, albumin,
gelatin, hemoglobin etc. have been studied for
medical & pharmaceutical applications. The use
of these polymers is limited because of their high
costs and questionable purity. Examples-Albumin,
Collagen, Gelatin, Starch etc.
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14. Bio- degradable polymers
2. Synthetic Bio-degradable polymers -These type of
polymers are preferred rather than natural bio-degradable
polymers due to their inertness and easy and cheap
formulation.
Synthetic bio-degradable polymers have following
advantages over natural ones :
• Localized delivery of drug.
• Sustain delivery of drug.
• Stabilization of drug.
• Reduced side effects etc.
Examples- Poly lactide homopolymer, Polyester,
L-PLA etc.
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15. Based on Linkage:
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Polyformaldehyde,
Polyesters,
Polycarbonates
Polyethylene,
HPLD Polyethylene
Natural rubber,
polyacrylamide gels,
epoxies, Alkyd resins
Epoxies,
Phenolformaldehyde

16. Based on Interaction with water
• Bio-degradable e.g. PAA
• Non-biodegradable e.g. PVC,PVA
• Slouble e.g. HPMC,PEG
• Hydrogel e.g. PVP
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17. GENERAL MECHANISM OF DRUG
RELEASE FROM POLYMER
• There are three primary mechanisms by which
active agents can be released from a delivery
system: namely,
• Diffusion
• Degradation
• Swelling followed by diffusion.
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18. Diffusion
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The system shown in Figure (a) is
representative of an implantable or
oral reservoir delivery system,
whereas the system shown in (b) is
transdermal system.

19. Bio degradation of polymers
• Chemical Erosion
• Physical Erosion
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20. Chemical Erosion
Bio erosions through chemical mechanisms are explained
below-
• Mechanism-I :It describes the degradation of water
soluble macromolecules that are cross-linked to form
three dimentional Network Degradation in these systems
can occur by:
Type (1A)- Degradation occur at crosslinks to form
soluble backbone polymeric chains. It provides high
molecular weight, Water soluble fragments.
Type (1B)- Degradation occur to form water-soluble
fragments. Such type provides low molecular weight, water
soluble oligomers and monomers.
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21. Chemical Erosion
Mechanism-II : Describes the dissolution of water
insoluble macromolecules with side groups that are
converted to water insoluble polymers as a result of
ionization, Protonation or hydrolysis of the groups.
• Molecular weight remains unchanged.
• Materials showing this type of erosion include:
Cellulose acetate derivatives,
Co-polymers of maleic anhydride.
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22. Chemical Erosion
Mechanism-III : Describes the degradation of
insoluble polymers with liable bonds. It forms
low molecular weight, water soluble molecules.
• Polymers undergoing this type of erosion
include:
Poly(lactic acids)
Poly(glycolic acid) and their co-polymers etc.
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23. Physical erosion
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• The physical erosion mechanisms can be characterized
as heterogeneous or homogeneous.
• Most polymers undergo homogenous erosion that
means the hydrolysis occur at even rate through out the
polymeric matrix.
• In homogenous erosion, there is loss of integrity of the
matrix or polymer.
• In heterogeneous erosion, also called as Surface Erosion.
The polymer erodes only at the surface and maintains its
physical integrity as it degrades.
• Highly crystalline polymers tend to undergo
heterogeneous erosion.

24. APPLICATIONS OF POLYMERS IN
CONTROLLED DRUG DELIVERY
1.ORAL DELIVERY SYSTEM:
• These techniques are capable of controlling the
rate of drug from the delivery systems that can
be utilized for controlled delivery of drugs.
• Some of novel drug delivery system for oral
controlled release drug administration include:
Osmotic pressure controlled GI delivery system.
Diffusion controlled GI delivery system.
Bio[muco]adhesive GI delivery system.
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25. Cont.
• Osmotic Pressure Controlled GI delivery
system: Semi permeable membrane made from
biocompatible polymers.
E.g. cellulose acetate
E.g. of such type of system include tablet which
contains Phenyl propanolamine as a drug.
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26. Cont.
• Gel diffusion controlled GI delivery
system: Fabricated from gel forming polymers
such as CMC.
• Bio adhesive GI drug delivery system:It is
capable of producing an adhesion interaction
with a biological membrane. E.g. Carbopol.
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27. 2.Transdermal drug delivery system:
Mostly used when the medicaments are applied on
topical route E.g. Transdermal patch of
scopolamine, nitro glycerin etc.
Advantages:
• They permits easy removal and termination of
drug action in situation of toxicity.
• Problems encountered with oral administration
like degradation, gastric irritation etc. are
avoided.
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28. 3.Ocular Drug Delivery System.
• It allows prolonged contact of drug with the
surface of the eye.
• Highly viscous suspension and emulsion are
prepared to have such purpose but these
preparations does not achieve this purpose at
controlled rate. E.g. Pilocarpine ocular insert
used in treatment of glaucoma.
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29. Other applications:
• Drug delivery and the treatment
of diabetes: Here the polymer will
act as a barrier between blood stream
and insulin. E.g. Polyacrylamide or
N,N-Dimethyl amino ethylmetha
acrylate.
• Drug delivery of various
contraceptives and hormones: It
consist of drug saturated liquid
medium encapsulated in polymeric
layer which controls the concentration
and release of drugs into the blood
stream. E.g. Medoxy progesterone
acetate, Progestasert, Duromine etc.
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30. Polymer Membrane Permeation-
Controlled Drug Delivery Systems
Various uses of Polymers in
pharmaceutical sciences:
1. Formulation of Matrix tablets.
2. Formulation of Nanoparticles.
3. Formulation of solid dispersion.
4. In targeted drug delivery
systems.
5. In the preparation of Polypeptide
vesicles for drug
delivery.
6. In formulation of cross linked
Polymers.
7. Micelles for cancer therapeutics.
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31. REFERENCES
• Targeted and control drug delivery by S.P.Vyas
and R.K.Khar. Pg. no 417 to 422.
• The eastern pharmacist-august,1998, vol. no 41.
• Remington : The science and practice of
pharmacy. Vol.no 1 [20th edition]
• Bio pharmaceutics and pharmacokinetics by
D.M.Brahmankar and Sunil.B.Jaiswal.
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32. Thank You
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