Polymers as excipients - Introduction to polymers, classification, important properties for applications, use of polymers in conventional formulations, modified /controlled release formulations, HPMC, Gelatin, Carbopol, Eudragit

1. Polymers as
excipients

2. Introduction
• Polymers are long chain organic molecules assembled from many
smaller molecules called as monomers.
• 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] -

3. Classification
• Based on origin :
• a) Natural Polymers :
e.g. Starch, cellulose
• b) Synthetic Polymers :
e.g. polyesters, polyanhydrides, polyamides
• Based on Bio-stability :
• a) Bio-degradable Polymers :
e.g. polyesters, carbohydrates, etc
• b) Non – biodegradable Polymers :
e.g. ethyl cellulose, HPMC, acrylic polymers, silicones

4. Classification
• Based on functional properties
• a)Thermosensitive polymers
• poly(N-isopropylacrylamide), poly(N-vinylcaprolactam) (PVCL)
• b)Mucoadhesive polymers
• polyacrylates, carboxymethyl cellulose, sodium salt and alginates
• c)Sorptive polymer
• Chitosan

5. Polymers in Conventional Dosage Forms
• Tablets :
- As binders
- To mask unpleasant taste
- For enteric coated tablets
• Liquids :
- Viscosity enhancers
- For controlling the flow
• In transdermal Patches
- Reservoir type
- Matrix type
• Ocusert System
- Matrix type

6. Polymers in Controlled Release (CR) formulations
(Mechanism of drug release)
• Diffusion controlled
• Reservoir type: the drug is contained in a core, which is surrounded by
a polymer membrane, and it is released by diffusion through this rate
controlling membrane. E.g. Poly(N-vinyl pyrrolidone)
• Matrix type: The drug is released either by passing through the pores
or between polymer chains. E.g. Polyvinylacetate
• Erosion controlled
• Polymer erode or degrade to release the drug. E.g poly(lactic acid),
poly(lactic-co-glycolic acid)

7. Diffusion controlled release (Reservoir type)

8. Diffusion controlled release (Matrix type)

9. Erosion controlled release

10. Polymers in Controlled Release (CR) formulations
• CR formulations utilize natural or synthetic polymers that provide CR
of the therapeutic agent via diffusion and/or erosion mechanism.
• The drug transport occur via diffusion
• The rate of release is controlled by mixing different polymers with
varying diffusion/erosion kinetics
• Generally natural polymers or their derivatives (such as cellulose and
methyl cellulose) as well as synthetic nondegradable polymers [such
as poly(vinyl pyrrolidone) and polymethacrylates] are used for oral
controlled release (CR) applications.

11. Important properties of the Polymers which
affect drug release kinetics in dosage form

12. Hydroxy Propyl Methyl Cellulose (HPMC)
• It is a semisynthetic, Inert, Viscoelastic polymer used as an
ophthalmic lubricant as well as an excipient and controlled
delivery component in oral medicaments. It is also found in
variety of commercial products.
• Description- It is solid and slightly off-white to beige powder in
appearance and may be formed in granules.
• Functional Category: Bioadhesive material; coating agent;
controlled-release agent; dispersing agent; dissolution enhancer;
emulsifying agent

13. Hydroxypropyl Methyl Cellulose (HPMC)
• Applications in Pharmaceutical Formulation: Hypromellose is widely
used in oral, ophthalmic, nasal, and topical pharmaceutical
formulations. In oral products, hypromellose is primarily used as a
tablet binder, in film-coating, and as a matrix for use in extended
release tablet formulations
• Method of Manufacture: Cellulose fibers obtained from cotton linters
or wood pulp are treated with caustic soda. Alkali cellulose thus
obtained is in turn treated with methyl chloride and propylene oxide
to produce methyl hydroxyl propyl esters of cellulose. Fibrous
reaction product is than purified and ground to fine uniform powder
or granules.
• Safety: Hypromellose is widely used as an excipient in oral,
ophthalmic, nasal, and topical pharmaceutical formulations. LD50
(mouse, IP): 5 g/kg

14. Eudragit (Polymethacrylates)
• Description: Polymethacrylates are synthetic cationic and anionic
polymers of dimethylaminoethyl methacrylates, methacrylic acid, and
methacrylic acid esters in varying ratios.
• Functional Category: Film-forming agent; tablet binder; tablet diluent
• Applications : Polymethacrylate copolymers are widely used as film-
coating materials in oral pharmaceutical formulations. Eudragit E is
used as a plain or insulating film former. Eudragit RL, RS, NE 30D, NE
40D are used to form water-insoluble film coats for sustained-release
products. Eudragit L-30, D-55 is used as an enteric coating film former
for solid-dosage forms
• Regulatory Status: Included in the FDA Inactive Ingredients Database
(oral capsules and tablets)

15. Carbopol (Carbomer)
• Functional Category: Bioadhesive material; controlled-release agent;
emulsifying agent; emulsion stabilizer
• Applications: Carbomers are used in liquid or semisolid
pharmaceutical formulations as viscosity modifiers. Formulations
include creams, gels, lotions and ointments for use in ophthalmic. In
tablet formulations, carbomers are used as controlled release agents
and/or as binders, sustained-release matrix beads.
• Safety: Carbomers are generally regarded as essentially nontoxic and
nonirritant materials. LD50 (mouse, oral): 4.6 g/kg for carbomer 934.
• Regulatory Acceptance: Included in the FDA Inactive Ingredients
Database (oral suspensions, tablets; ophthalmic, rectal, topical,
transdermal preparations; vaginal suppositories)

16. Gelatin
• Description: Gelatin occurs as a light-amber to faintly yellow-colored,
vitreous, brittle solid. It is practically odorless and tasteless, and is
available as translucent sheets, flakes, and granules. Gelatin is
extracted from animal tissues rich in collagen such as skin and bone
• Functional Category: Coating agent; film-forming agent; gelling agent;
suspending agent; tablet binder; viscosity-increasing agent.
• Applications : Gelatin is widely used in a variety of pharmaceutical
formulations, including its use as a biodegradable matrix material in
an implantable delivery system, although it is most frequently used to
form either hard or soft gelatin capsules.
• Safety: Gelatin may be regarded as a nontoxic and nonirritant
material. LD50 (rat, oral): 5 g/kg
• Regulatory Status: GRAS listed.

17. References
• Rowe, R. C., Sheskey, P. J., & Owen, S. C. (Eds.)Handbook of
pharmaceutical excipients (6th ed.). London: Pharmaceutical Press
and A.A.P.S., 2009
• Kadtare A. and Mahesh Chaube, Excipient Development for
Pharmaceutical, Biotechnology and Drug Delivery Systems, Informa
Healthcare USA, Inc. 270 Madison Avenue, New York 10016, 2006
• Rudnic, E. M., & Schwartz, J. D. ,Remington: The Science and Practice
of Pharmacy, (A. R. Gennaro, Ed.) Philadelphia: Lippincott Williams &
Wilkins, 2006

18. Thank You