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Activation modulated drug delivery systems
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  • 1. 1
  • 2. CLASSIFICATION Rate pre-programmed drug delivery systems Activation – modulated drug delivery systems Feedback- regulated drug delivery systems Site- targeting drug delivery systems 2
  • 3. ACTIVATION MODULATED DDS Drug delivery is activated and controlled by physical, chemical or bio-chemical processes or facilitated by the energy supplied externallyClassification of activation modulated DDS Based on the nature of the process applied or the type of energy used1. Physical means2. Chemical means3. Biological means 3
  • 4. DDS activated by physical meansa. Osmotic pressure- activated DDSb. Hydrodynamic pressure activated DDSc. Vapour pressure activated DDSd. Mechanically activated DDSe. Magnetically activated DDSf. Sonophorosis activated DDSg. Iontophoresis activated DDSh. Hydration activated DDS 4
  • 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) /hmPw = water permeabilityAm = effective surface areahm =thickness of the semi permeable housing 5
  • 6. Vasopressin 6
  • 7. 2. Hydrodynamic pressure activated DDS hydrodynamic pressure is used as the source of energy to activate the drug release. 7
  • 8. Q/t = Pf Am/hm (θs – θe)Pf = fluid permeabilityAm = effective surface areahm = thickness of the wall with annular openingsθs – θe = difference in hydrodynamic pressure between the DDS and the environment 8
  • 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) 9
  • 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. inletseptum for percutaneous refill of infusate, 9. needle stop. 10
  • 11. Q/t= d4(Ps-P-e)/40.74µld & l = the inner diameter and the length of the delivery cannula, respectivelyPs-P-e = difference between the vapour pressure in the pumping compartment and the site of implantation.µ = viscosity of the drug formulation used. 11
  • 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). 12
  • 13. 13
  • 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 14
  • 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 albumin6. 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]. 15
  • 16. Sonophoresis-activated drug delivery systems 16
  • 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 17
  • 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 18
  • 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. 19
  • 20.  release of the drug is controlled by matrix diffusion through this gel barrier 20
  • 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 21
  • 22. ***Thank You!*** 22