Information about Pharmaceutical polymers and their properties used in different sector in a pharmaceutical company.

2. 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.

3. 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.

4.  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] -

5. 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.

6. 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.

7. 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.

8. 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.

9. 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

10.  Reservoir Systems
- Ocusert System
- Progestasert System
- Reservoir Designed Transdermal Patches
 Matrix Systems
 Swelling Controlled Release Systems
 Biodegradable Systems
 Osmotically controlled Drug Delivery

11. 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, and swelling followed by
diffusion
 Any or all of these mechanisms may occur in a given
release system
 Diffusion occurs when a drug or other active agent
passes through the polymer that forms the controlled-
release device. The diffusion can occur on a
macroscopic scale as through pores in the polymer
matrix or on a molecular level, by passing between
polymer chains

12. Drug release from typical matrix
release system

13.  For the reservoir systems the drug delivery rate can
remain fairly constant.
 In this design, a reservoir whether solid drug, dilute
solution, or highly concentrated drug solution within a
polymer matrix is surrounded by a film or membrane
of a rate-controlling material.
 The only structure effectively limiting the release of
the drug is the polymer layer surrounding the
reservoir.
 This polymer coating is uniform and of a nonchanging
thickness, the diffusion rate of the active agent can be
kept fairly stable throughout the lifetime of the
delivery system. 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 .

14. Drug delivery from typical
reservoir devices: (a) implantable
or oral systems, and (b)
transdermal systems.

16. ENVIRONMENTALLY RESPONSIVE SYSTEM
 It is also possible for a drug delivery system to be
designed so that it is incapable of releasing its agent or
agents until it is placed in an appropriate biological
environment.
 Controlled release systems are initially dry and, when
placed in the body, will absorb water or other body
fluids and swell,
 The swelling increases the aqueous solvent content
within the formulation as well as the polymer mesh
size, enabling the drug to diffuse through the swollen
network into the external environment.

17. Drug delivery from (a) reservoir and (b)
matrix swelling-controlled release systems.

18. BIO DEGRADABLE POLYMER
 Biodegradable polymers can be classified in two:
 Natural biodegradable polymer
 Synthetic biodegradable polymer
 Synthetic biodegradable polymer are preferred more
than the natural biodegradable polymer because they
are free of immunogenicity & their physicochemical
properties are more predictable &reproducible

19. 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)

20.  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.

21. DRUG RELEASE MECHANISM FROM
BIOERODIBLE POLYMERS
 The release of drugs from the erodible polymers occurs
basically by three mechanisms,
I. The drug is attached to the polymeric backbone by a
labile bond, this bond has a higher reactivity toward
hydrolysis than the polymer reactivity to break down.
II. The drug is in the core surrounded by a biodegradable
rate controlling membrane. This is a reservoir type
device that provides erodibility to eliminate surgical
removal of the drug-depleted device.
III. a homogeneously dispersed drug in the biodegradable
polymer. The drug is released by erosion, diffusion, or a
combination of both.

22. Schematic representation of drug release mechanisms In mechanism 1, drug is released by hydrolysis of polymeric bond.
In mechanism 2, drug release is controlled by biodegradable membrane. In mechanism 3, drug is released by erosion,
diffusion, or a combination of both

23. POLYMER EROSION MECHANISM
 The term 'biodegradation' is limited to the
description of chemical processes (chemical
changes that alter either the molecular weight or
solubility of the polymer)
 ‘Bioerosion' may be restricted to refer to physical
processes that result in weight loss of a polymer
device.
 The erosion of polymers basically takes place by two
methods:-
1. Chemical erosion
2. Physical erosion

24. CHEMICAL EROSION
 There are three general chemical mechanisms that cause
bioerosion
1. The degradation of water-soluble macromolecules that
are crosslinked to form three-dimensional network.
As long as crosslinks remain intact, the network is intact
and is insoluble.
Degradation in these systems can occur either at
crosslinks to form soluble backbone polymeric chains
(type IA) or at the main chain to form water-soluble
fragments (type IB). Generally, degradation of type IA
polymers provide high molecular weight, water-soluble
fragments, while degradation of type IB polymers provide
low molecular weight, water soluble oligomers and
monomers

26. 2. The dissolution of water-insoluble macromolecules
with side groups that are converted to water-soluble
polymers as a result of ionization, protonation or
hydrolysis of the groups. With this mechanism the
polymer does not degrade and its molecular weight
remains essentially unchanged. E.g. cellulose acetate
3. The degradation of insoluble polymers with labile
bonds. Hydrolysis of labile bonds causes scission of
the polymer backbone, thereby forming low
molecular weight, water-soluble molecules. E.g. poly
(lactic acid), poly (glycolic acid)
The three mechanisms described are not mutually
exclusive; combinations of them can occur.