Transcript Polymeric Sciences

Polymeric Sciences
Dr. Basavaraj K. Nanjwade
M. Pharm., Ph. D
Department of Pharmaceutics
Faculty of Pharmacy
Omer Al-Mukhtar University
Tobruk, Libya.
E-mail: [email protected]
2014/01/26
Faculty of Pharmacy, Omer Al-Mukhtar University,
Tobruk, Libya.
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CONTENTS
1.
2.
3.
4.
5.
6.
Definition and Types of polymers.
Properties of Polymers.
Drug-Polymer Interactions.
Polymers in Pharmaceutical preparation.
Viscosity of polymer solutions.
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 manufacturing of bottles, syringes, vials,
catheters, and also in drug formulations.
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Definition
• “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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Definition
• 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] -
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Types of polymers
A. Based on origin :
a) Natural Polymers :
e.g. Proteins – Collagen, Keratin, Albumin
Carbohydrates – starch, cellulose, glycogen.
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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Types of polymers
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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Types of polymers
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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Properties of Polymers
• 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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Properties of Polymers
• It must be soluble and easy to synthesize; must
have a finite molecular weight.
• 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.
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Drug-Polymer Interactions
Biodegradable polymer for ocular , nonviral DNA ,
tissue engineering , vascular , orthopedic , skin adhesive
& surgical gloves.
Biodegradable polymer lens materials that could ensure the
proper delivery of medicine for treating glaucoma, chronic dry
eye, corneal ulcers and other ocular ailments.
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Polymers in Pharmaceutical
preparation
• 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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Polymers in Pharmaceutical
preparation
• 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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A. Reservoir System :
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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A. Reservoir System :
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A. Reservoir System :
 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 beadhesive
polymer.
e.g. Silicone Polymer, Polyacrylates.
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Transdermal Patches :
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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 biodegradation 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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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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Biodegradable Polymers
• 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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Mechanism of Biodegradation
• 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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Tobruk, Libya.
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Biodegradable Polymers
• 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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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- tobatch reproducibility and purity of the sample.
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Natural Polymers
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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Natural Polymers
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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Viscosity of polymer solutions
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References
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Novel drug delivery systems - Y. W. Chien-Dekker 50
Bio–adhesive drug delivery system-Dekker 98
Encyclopedia of controlled drug delivery systems.
Controlled release of biologically active agentsRichard baker
Polymer in control drug delivery edited by Lisbeth
Lillum and Stanley S. Davis
www.google.com
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THANK YOU
E-mail: [email protected]
2014/01/26
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Tobruk, Libya.
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