Transcript By : Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D KLE University’s College of Pharmacy BELGAUM – 590010, Karnataka, India Cell No: 00919742431000 E-mail:

By :
Prof. Dr. Basavaraj K. Nanjwade M. Pharm., Ph. D
KLE University’s College of Pharmacy
BELGAUM – 590010, Karnataka, India
Cell No: 00919742431000
E-mail: [email protected]
CONTENTS
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Introduction
Classification of Polymers
Applications in Conventional Dosage Forms
Applications in Controlled Drug Delivery
Biodegradable Polymers
Natural Polymers
References
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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.
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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.
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• 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] 07/09/2010
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CLASSIFICATION
A. Based on origin :
a) Natural Polymers :
e.g. Proteins – Collagen, Keratin, Albumin
Carbohydrates – starch, cellulose,
glycogen.
DNA, RNA
b) 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.
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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.
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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.
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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.
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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 nonantigenic.
• Should be biodegradable or be eliminated
from body after its function is over.
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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
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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
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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.
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
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.
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
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.
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Transdermal
DrugDelivery
Delivery
TransdermalControlled
Controlled Drug
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B. Osmotically Controlled Drug
Delivery System
• Drug is coated with semipermeable polymer
e.g. Cellulose acetate.
• Water generates osmotic
pressure gradient by
permeating through semipermeable membrane.
• Due to that drug pumps
out of delivery orifice over
a prolonged time at a
defined rate.
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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.
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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.
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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.
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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
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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.
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
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
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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)
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• 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.
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-
• 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
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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.
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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 batchto-batch reproducibility and purity of the
sample.
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•
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.
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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.
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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
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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.
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Muco–Adhesive 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.
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REFERENCES
• Novel drug delivery systems – Y.W.Chien –
Dekker 50
• Eastern Pharmacist – April, 2001.
August, 1998
• Bio–adhesive drug delivery system –
Dekker 98
• Encyclopedia of controlled drug delivery
systems.
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Cell No: 00919742431000
E-mail: [email protected]
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