The document discusses various approaches for developing sustained release and controlled release drug delivery systems. It describes biological factors that influence drug release such as half-life and metabolism. It also discusses physicochemical properties like solubility, partition coefficient, and stability. The mechanisms of drug release include diffusion systems, dissolution systems, ion exchange resins, osmotic systems, and erosion systems. Diffusion systems are typically matrix or reservoir based while dissolution systems can be encapsulated or matrix types. Osmotic systems use a semi-permeable membrane to pump out drug solution through a delivery aperture. Erosion systems can degrade through either bulk or surface erosion.

1. SUSTAINED AND CONTROLLED
RELEASE DRUG DELIVERY
SYSTEMS
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By : Dr. Umesh Kumar Sharma and Arathy .S.A
Department of Pharmaceutics,
Mar Dioscorus College of Pharmacy,
Alathara, Sreekariyam,
Thiruvananthapuram, Kerala, India

2. BIOLOGICAL & PHYSICOCHEMICAL
APPROACHES FOR SR / CR FORMULATION
BIOLOGICAL:
Half Life:
Therapeutic compounds with short half life are
excellent products for SR formulation.
Half life is the time taken for the amount of
drug to fall by half and is determined by the
clearance (cl) and volume of distribution (vd).
t½ = 0.693 vd / cl 2
SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

3. YH
Absorption:
 The rate of release is much slower than the rate of absorption.
kr<<<ka
Metabolism of drug:
The drugs that are considerably metabolized before
absorption either in the tissue or the intestine can show
decreased bioavailability..
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

4. Dose size:
 A single dose of 0.5g - 1.0g is considered maximum for a
conventional dosage form. This also holds true for sustained
release dosage form.
 Compounds that require large dosing size can sometimes be
given in multiple amounts or formulated into liquid systems.
4SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

5.  Ionization, pka and Aqueous solubility:
 The drug in an unchanged form is advantage for drug
permeation.
 Compounds with low solubility are inherently sustained.
 Partition coefficient:
 Compounds which are lipophilic in nature having high
partition coefficient.
 The ability of a drug to penetrate these lipid membranes is its
apparent oil/water partition coefficient (k), defined as
k=co/cw
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

6. Stability
 The dosage form that is unstable in stomach
systems that prolong delivery over the entire
course of transit in gastrointestinal tract are
beneficial.
 Compounds that are unstable in small intestine
may demonstrate decreased bioavailability.
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

7. DRUG RELEASE MECHANISM OF SUSTAINED
AND CONTROLLED RELEASE DRUG DELIVERY
SYSTEM
Diffusion systems
 Movement of drug molecules from a region of
a higher concentration to lower concentration.
 No energy required for this.
They are typically either matrix based or
reservoir diffusion systems.
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

8. a. Reservoir system.
 A water insoluble polymeric material covers
a core of drug.
 According to fick’s law
J = -D/dc/dx
b. Matrix system.
 A well mixed composite of one or more
drugs with gelling agent.
 Amount of drug release is given by
Higuchi’s equation
Q = Dϵ/T(2A.ECs)Cs.t)1/2
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

9. RESERVOIR AND MATRIX SYSTEMS
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

10. 2. Dissolution systems
 A drug with a slow dissolution rate is inherently sustained.
 Commonly employed in the production of enteric coated dosage
forms.
Flow rate of the material is given by
Noyer Whitney equation
KA (Cs-Cb)
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0SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

11. a. Encapsulated dissolution system
 The maintenance dose of drug can be achieved by applying
thicker coating.
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SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

12. b. Matrix dissolution system
 These can be prepared by compressing the drug with slowly
soluble polymer carrier into a tablet.
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2SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

13. Ion exchange resins system
 They are cross linked water insoluble polymers carrying
ionisable functional groups.
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3SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

14. Osmotic system:
 A semi permeable membrane is placed
around a tablet, drug solution that allows
transport of water into the tablet with
eventual pumping of drug solution out
of tablet through a small delivery
aperture in tablet coating.
 The rate of release is given by
Q/t= pW AM (πS-πC)/hm 1
4SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

15. 1
5SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

16. Erosion system:
 Drug or active ingredient are mixed with
biodegradable polymers.
 The release of the drug, typically from a
bulk phase.
 The changes of bulk phase can be
segregated into two distinct categories bulk
erosion and surface erosion.
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6SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

17. a. Bulk erosion
The material degrades or deforms uniformly
throughout the bulk of the material.
b. Surface erosion
The material degrades from the outer
surface inward uniformly only at the
interface between the bulk of the material
and the surrounding environment.
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7SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

18. 1
8SR & CR, By : Dr. Umesh Kumar Sharma and Arathy .S.A

19. THANK YOU
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By : Dr. Umesh Kumar Sharma and
Arathy .S.A
Department of Pharmaceutics,
Mar Dioscorus College of Pharmacy,
Alathara, Sreekariyam,
Thiruvananthapuram, Kerala, India