This document summarizes different mechanisms of drug release from delivery systems. There are three main types of mechanisms: dissolution controlled, diffusion controlled, and dissolution/diffusion controlled. Dissolution controlled systems release drug through the dissolution of a coating or matrix that encapsulates or embeds the drug. Diffusion controlled systems release drug through diffusion out of an inert membrane barrier. Dissolution/diffusion controlled systems combine aspects of both mechanisms, as the drug core is encased in a partially soluble membrane through which aqueous medium can enter to dissolve the drug and pores in the membrane allow dissolved drug to diffuse out over time. These controlled release mechanisms aim to improve drug delivery to the body.

1. MECHANISM OF DRUG RELEASE
Presented by :-
Pravin B. Dhas
M. Pharm 1st year
Department of Pharmaceutics

2.  Introduction to Drug Release
 Types of delivery systems
 Types of Mechanism
Dissolution controlled system
Diffusion controlled system
Dissolution & diffusion controlled
system

3. Drug release refers to the process by which the drug loaded
in or released in the body through diffusion or dissolution
OR after biodegredation of DRUG DELIVERY DEVICE.
Controlled Release Mechanisms
These are developed
1-To improve the temporal and spatial presentation of
drug in the body
2-To protect drug from physiological degradation or
elimination
3-To improve patient compliance and to enhance
quality control in manufacturing of drug products.

4.  On basis of technical sophistication
Rate programmed DDS
1-Dissolution controlled DDS
2-Diffusion controlled DDS
3-Disso. & diffusion controlled DDS
Stimuli-activated DDS
Site targated DDS

5. 1-Reservoir
2-Matrix
1-
Encapsulation
2-Matrix

6. A-DISSOLUTION CONTROLLED
SYSTEMS
The rate controlling step is dissolution.
The drug is embedment in slowly
dissolving or erodible matrix or by coating
with slowly dissolving substances.
It is of two types:-
1 Encapsulation dissolution controlled
system
2-Matrix dissolution controlled system

7. The drug particles are coated or encapsulated by
microencapsulation techniques with slowly
dissolving materials (
like cellulose, polyethylene glycols,
polymethacrylates, waxes etc.
The dissolution rate of coat depends upon the
solubility
and thickness of the coating.
1-ENCAPSULATION DISSOLUTION
CONTROLLED SYSTEMS :-

8. 2-MATRIX DISSOLUTION CONTROLLED
SYSTEMS :-
Matrix systems are also called as monoliths since
the drug is homogeneously dispersed throughout a
rate controlling medium.
They employ waxes such as beeswax, carnauba
wax, hydrogenated castor oil etc which control drug
dissolution by controlling the rate of dissolution fluid
penetration into the matrix by altering the porosity of
rate.
The wax embedded drug is generally prepared by
dispersing the drug in molten wax and congealing
and

10. B-DIFFUSION
CONTROLLED RELEASE
SYSTEMS:-Diffusion systems are characterized by release rate of
drug is dependant on its diffusion through inert water
insoluble membrane barrier.
These are of two types:-
a) Porous matrix-controlled system
b) Porous-membrane controlled
system

12. C-DISSOLUTION AND DIFFUSION
CONTROLLED RELEASE SYSTEMS
The drug core is encased in a partially soluble
membrane. Pores are thus created due to dissolution
of parts of the membrane which
1- Permit entry of aqueous medium into the core
and hence drug dissolution occurs
2- Allow diffusion of dissolved drug out of the
system

14. REFERANCES:-
 Brahmankar. Biopharmaceutics and pharmacokinetics .
fifth edition, pg: 350-25
 Edith Mathiowitz. Encyclopedia of controlled drug
delivery.
1sted, Vol.II, pg: 698-29.
 Wise DL. Hand book of pharmaceutical controlled release
technology. First edition, pg: 183-24.
 Tamizharasi S, Rathi JC, Rathi V. Formulation and
evaluation of Pentoxifylline-loaded Poly(ἑ-caprolactone)
microspheres . Ind J of Pharm Sci, 2008may; 70(3):333-5.