This document discusses polymers used in drug delivery. Polymers are macromolecules made of repeating monomer units. They can be classified based on monomer type, arrangement, structure, properties, source, form, and biodegradability. Copolymers contain two monomers, while homopolymers contain one. Polymers have applications in conventional dosage forms like tablets and liquids, as well as controlled drug delivery systems. Biodegradable polymers break down in response to chemical reactions like hydrolysis. Their degradation can be hydrolytic, enzymatic, and affected by various factors.

1. Polymers in Drug Delivery

2. Polymer
“Polymer” word is derived from Greek roots “Polus” meaning
many and “Meros” meaning parts.
Definition :
Polymers are high molecular weight chemical compounds
(macromolecules) assembled from a large number of
repeating units called as monomers.

3. Classification of polymers
1. Based on nature of monomers
a) Homopolymers
b) Copolymers
2. Based on the arrangement of monomers
a) Random copolymers
b) Graft copolymers
c) Block copolymers
3. Based on the structure of the polymers
a) Linear
b) Branched
c) Cross-linked
4. Based on thermal response and polymer
property
a) Thermoplastics
b) Thermosets
c) Elastomers
5. Based on the source
a) Natural Polymers
b) Semisynthetic polymers
c) Synthetic polymers

4. 6. Based on the form and use
a) plastics
b) Elastomers
c) Fibers
d) Liquid resins
7. Based on bio-stability
a) Biodegradable polymers e.g. polyesters, proteins,
carbohydrates
b) Non-biodegradable polymers e.g. ethyl cellulose,
HPMC, acrylic polymers, silicones.

5.  Copolymer:
Polymer formed from two or more different monomers is called as
copolymer.
- [A – B – A – B – A – B] –
 Homopolymer:
Polymer formed from bonding of identical monomers is called as
homopolymer.
- [A – A – A – A – A] –

6. Characteristics for Ideal Polymer
 Should be inert and compatible with theenvironment.
 Should benon-toxic.
 Should be easilyadministered.
 Should be easy and inexpensive tofabricate.
 Should have good mechanicalstrength.
 Should provide drug attachment and release sites for drug
polymer linkages.

7. Applications in Conventional Dosage Forms
 Tablets :
- As binders
- Tomask unpleasant taste
- For enteric coated tablets
 Liquids:
- Viscosity enhancers
- For controlling the flow
 Semisolids :
- In the gel preparation
- In ointments
 In transdermal Patches

8. 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

9. 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.

10.  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

11. Mechanism of Biodegradation
A. Hydrolytic Degradation :
Breakdown of polymer by water by cleaving long
chain into monomeric acids. This is done by two
ways:
a)Bulk eroding polymers e.g. Polylactic acid
(PLA),Polyglycolic acid (PGA)
b) 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.

12. Factors affecting Biodegradation
 Polymermorphology
 pH & ionicstrength
 Drug – polymer interaction
 Chemical composition andstructure
 Processing methods andconditions
 Presence of chain defects