This document discusses different types of activation modulated drug delivery systems (DDS). It describes DDS that are activated by physical, chemical, or biological means. Some examples of physically activated DDS include osmotic pressure-activated, hydrodynamic pressure-activated, vapour pressure-activated, and mechanically activated systems. Magnetically activated and sonophorosis activated DDS are also mentioned. The document provides details on the mechanisms and equations for rate of drug release for some of these systems. It further discusses iontophoresis-activated and hydration-activated DDS and provides one example for each.

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2. CLASSIFICATION
 Rate pre-programmed drug delivery systems
 Activation – modulated drug delivery systems
 Feedback- regulated drug delivery systems
 Site- targeting drug delivery systems
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3. ACTIVATION MODULATED DDS
 Drug delivery is activated and controlled by physical,
chemical or bio-chemical processes or facilitated by the
energy supplied externally
Classification of activation modulated DDS
 Based on the nature of the process applied or the type
of energy used
1. Physical means
2. Chemical means
3. Biological means
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4. DDS activated by physical means
a. Osmotic pressure- activated DDS
b. Hydrodynamic pressure activated DDS
c. Vapour pressure activated DDS
d. Mechanically activated DDS
e. Magnetically activated DDS
f. Sonophorosis activated DDS
g. Iontophoresis activated DDS
h. Hydration activated DDS
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5. 1. Osmotic pressure- activated DDS
 drug reservoir can be a solution contained within an
impermeable collapsable tube.
 This is covered with osmotic agent place in a rigid semi
permeable housing with controlled water permeability.
 The rate of drug release is modulated by the gradient of
osmotic pressure.
Q/t = PwAm (πs-πe) /hm
Pw = water permeability
Am = effective surface area
hm =thickness of the semi permeable housing
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6. Vasopressin
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7. 2. Hydrodynamic pressure activated DDS
 hydrodynamic pressure is used as the source of energy
to activate the drug release.
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8. Q/t = Pf Am/hm (θs – θe)
Pf = fluid permeability
Am = effective surface area
hm = thickness of the wall with annular openings
θs – θe = difference in hydrodynamic pressure between the
DDS and the environment
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9. 3. Vapour pressure- activated drug delivery systems
 Drug inside infusion compartment is separated from
pumping compartment by freely movable partition.
 Pumping compartment contains a fluorocarbon
fluid that vaporizes at body temperature
 The vapour pressure created moves the partition
upward, forcing the drug to be delivered.
 Eg: INFUSAID implants (heparin)
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10. 1. Flow regulator, 2. silicone polymer coating, 3. patrition,
4. Pumping compartment, 5. Infusate compartment, 6.
fluorocarbon fluid filling tube, 7. filter assembly, 8. inlet
septum for percutaneous refill of infusate, 9. needle stop.
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11. Q/t= d4(Ps-P-e)/40.74µl
d & l = the inner diameter and the length of the delivery
cannula, respectively
Ps-P-e = difference between the vapour pressure in the
pumping compartment and the site of
implantation.
µ = viscosity of the drug formulation used.
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12. 4. Mechanically activated drug delivery system
 Equipped with a mechanically activated pumping system
 A measured dose of drug formulation is reproducibly
delivered
 The volume of solution delivered is controllable, as small as
10-100µl
 Volume of solution delivered is independent of the force &
duration of activation applied as well as the solution volume
in the container.
 Example is the development of metered dose nebulizer for
the intranasal administration of a precision dose of buserelin
(LHRH).
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14. 5. Magnetically activated drug delivery systems
 Drug reservoir is a dispersion of peptide or protein
powders in a polymer matrix
 Low rate of delivery is improved by incorporating
electromagnetically triggered vibration mechanism
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15.  Coating polymer can be a ethylene-vinyl acetate
copolymer or silicon elastomers.
 These systems have been used to deliver protein drugs,
such as bovine serum albumin
6. Sonophoresis-activated drug delivery systems
 Utilize ultrasonic energy to activate the delivery of the
drugs from a polymeric drug delivery device
 can be fabricated from either a non degradable
polymer, such as ethylene-vinyl acetate copolymer,
a bio erodible polymer such as poly[bis(p-
carboxyphenoxy)alkane anhydride].
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16. Sonophoresis-activated drug delivery systems
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17. 7. Iontophoresis-activated drug delivery systems
 uses electrical current to activate and to modulate
the diffusion of a charged drug molecule across
the skin in a facilitated rate
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18.  skin permeation rate of a charged molecule i consist of 3
components
Jiisp = Jp+Je+Jc
Jp = passive skin permeation flux
Je = electrical current driven permeation flux
Jc = convection flow-driven skin permeation flux
 IONSYS - fentanyl iontophoretic transdermal system
 Example : development of an iontophoretic DDS of
dexamethasone sodium phosphate
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19. 8. Hydration-activated drug delivery system
 Depends on the hydration induced swelling process to
activate the release of drug
 Drug reservoir is homogeneously dispersed in a swellable
polymer matrix fabricated from a hydrophilic polymer
 Release of the drug is controlled by the rate of swelling of
the polymer matrix.
 Example is VALRELEASE tablet- diazepam in hydrocolloid
and pharmaceutical excipients.
 In stomach absorbs the gastric fluid & forms colloidal gel
that starts from the tablet surface and grows inward.
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20.  release of the drug is controlled by matrix diffusion
through this gel barrier
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21. REFERENCES
 NOVEL DRUG DELIVERY SYSTEMS, 2nd edition, Yie W.
Chien
 CONTROLLED DRUG DELIVERY- FUNDAMENTALS AND
APPLICATIONS, 2nd edition, edited by Joseph R.
Robinson and Vincent H. L. Lee
 http://www.rxlist.com/ionsys-drug.htm
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22. ***Thank You!***
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