Polymeric Sciences

2014/01/26 1Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

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

Department of PharmaceuticsFaculty of Pharmacy

Omer Al-Mukhtar UniversityTobruk, Libya.

E-mail: nanjwadebk@gmail.com

CONTENTS

1. Definition and Types of polymers.2. Properties of Polymers.3. Drug-Polymer Interactions. 4. Polymers in Pharmaceutical preparation.5. Viscosity of polymer solutions.6. 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 polymersA. 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 polymersD. 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 InteractionsBiodegradable 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 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.

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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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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 BiodegradationA. 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.

2014/01/26 26Faculty of Pharmacy, Omer Al-Mukhtar University, Tobruk, Libya.

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- to-

batch reproducibility and purity of the sample.

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Natural Polymers1) 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. 2014/01/26 29Faculty of Pharmacy, Omer Al-Mukhtar University,

Tobruk, Libya.

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 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 agents-

Richard baker Polymer in control drug delivery edited by Lisbeth

Lillum and Stanley S. Davis www.google.com

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E-mail: nanjwadebk@gmail.com

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THANK YOU