Mechanism of dds1

Presented By : Facilitated To:
Sachin.J.Gaddimath Dr. Anita Desai
M.Pharm 1st year HOD and Professor
Dept. of Pharmaceutics Dept. of Pharmaceutics
HSKCOP, BAGALKOT. HSKCOP, BAGALKOT
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CONTENTS
 Introduction
 Differences between SR &CR Formulations
 Mechanism
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 Sustained Release: It is a drug delivery system that
achieve slow release of drug over an extended period
of time after administration of single dose usually 8-12
hours.
 Controlled Release: It is the delivery of the drug at a
predetermined rate or to location according to the
needs of the body and disease states for a definite
period of time.
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 Differences:
Sustained release dosage form Control release dosage form
It constitutes the dosage form that
provides medication over extended
period of time.
It constitutes the dosage form that
maintains constant drug levels in
blood or tissue.
It do not releases zero order kinetics. It releases zero order kinetics by
blood target tissue.
It may not be control. It may be control.
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MECHANISM OF DRUG DELIVERY:
 Dissolution controlled release.
A. Matrix dissolution control
B. Encapsulation dissolution control
 Diffusion controlled release.
A.Reservoir device
B.Matrix device
 Diffusion and Dissolution controlled release.
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DISSOLUTION CONTROLLED:
 Matrix dissolution control:
 Matrix dissolution devices are prepared by
compressing the drug with slowly dissolving carrier
into tablet.
 Matrix dissolution is controlled is by:
1. Altering porosity of tablet.
2. Decreasing its wettability.
3. Dissolving at slower rate.
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DRUG POLYMER MATRIX FORMULATION:
 There are 2 methods for preparing drug polymer
particles- congealing and aqueous dispersion method.
 The drug release is determined by dissolution rate of
the polymer.
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Encapsulation Dissolution Control:
 The drug particle are coated or encapsulated by
microencapsulation technique.
 The pellets are filled in hard gelatine capsule, popularly
called as ‘spansules’.
 Once the coating material dissolves the entire drug inside
the microcapsule it is immediately available for dissolution
and absorption.
 Here the drug release is determined by dissolution rate
and thickness of polymer membrane which may range
from 1 to 200µ.
 Dissolution rate of coat depends upon stability & thickness
of coating.
Examples:
1. Ornade spansules.
2. Cloro trimeton Repetabs.
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 MATERIALS USED FOR COATING OF SUSTAINED
RELEASE DOSAGE FORMS (ENCAPSULATION):
 Mixtures of waxes [bees wax, carnauba wax, etc] with
glycerol monostearate , stearic acid , glyceryl mono
palmitate and cetyl alcohol. These provide coatings
that are dissolved slowly or broken down in the GIT.
 Shellac and zein – polymers that remain intact until
the pH of the GI contents become less acidic.
 Ethyl cellulose, which provides a membrane around
the dosage form and remains intact throughout the
GIT. However, it does permit water to permeate the
film, dissolve the drug , and diffuse out again.
 Acrylic resins , which behave similarly to ethyl
cellulose as a diffusion controlled drug release coating
material.
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DIFFUSION CONTROLLED:
 This system is hollow containing an inner core of drug.
 The water insoluble polymeric material surrounds drug
reservoir.
 The drug partitions into the membrane and exchanges with
the surrounding fluid by diffusion.
 The release of drug from a reservoir device follows Fick’s
first law of diffusion.
J = D dc/dx
Where,
J = flux, amount/area-time
D = diffusion coefficient of drug in the polymer,
area/time
dc/dx = change in conc. with respect to polymer
distance
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 TYPES:
 There are 2 types of diffusion control:
 RESERVOIR DEVICES:
 Spherical type
 Slab type
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Rate controlling steps :
 Polymeric content in coating,
 Thickness of coating,
 Hardness of microcapsule.
The drug core is encased by a water-insoluble
polymeric materials.
The rate of drug release is dependent on the rate of
drug diffusion but not on the rate of dissolution.
In short, mass transport phenomena at molecular
level occurs.
Examples: Nico-400, Nitro-Bid
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Method of preparation of reservoir devices:
There are 2 methods:
 Coated Beads/Pellets
 Microencapsulation
Coated Beads/Pellets:
 Coating of drug solution onto preformed cores.
 Covering of core by an insoluble but permeable coat .
NOTE: Pan coating or air-suspension technique is
generally used for coating.
Pore forming additives may be added to the
coating solution.
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MICROENCAPSULATION:
 This technique used to encapsulate small particles of
drug, solution of drug, or even gases in a coat (usually
a polymer coat).
 Generally, any method that can induce a polymer
barrier to deposit on the surface of a liquid droplet or a
solid surface can be used to form microcapsules.
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Matrix Devices:
 A matrix or monolithic device consists of an inert
polymeric matrix in which a drug is uniformly distributed.
 Drugs can be dissolved in the matrix or the drugs can be
present as a dispersion.
NOTE : Matrix may be HOMOGENEOUS or POROUS with
water filled pores.
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 Rigid Matrix Diffusion :
1. Materials used are insoluble plastics such as PVP
& fatty acids.
 Swellable Matrix Diffusion :
1. Also called as Glassy hydro gels. Popular for
sustaining the release of highly water soluble drugs.
2. Materials used are hydrophilic gums.
Examples : Natural- Guar gum, Tragacanth.
Semi synthetic -HPMC, CMC, Xanthum gum.
Synthetic - Polyacrilamides.
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 DISSOLUTION AND DIFFUSION CONTROLLED RELEASE:
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 Drug is encased in a partially soluble membrane.
 Pores are created due to dissolution of parts of
membrane .
 It permits entry of aqueous membrane into pores &
drug dissolution.
 Hence it leads to diffusion of dissolved drug out of the
system .
 Example - Ethyl cellulose and PVP mixture dissolves in
water and create pores of ethyl cellulose membrane .
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REFERENCES:
Leon lachmann – The theory and
practical of industrial pharmacy.
 N.K. Jain – Controlled & novel drug
delivery.
www.google.com
Remington’s pharmaceutical sciences.
 Sustained and controlled release
systems.
-James W Robinson.
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Mechanism of dds1

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