Drug Delivery Systems Drug Delivery Systems container body drug Definition drug delivery systems

							Drug Delivery Systems

          container
              +       body
            drug
     Definition: drug delivery systems
  • Biomaterials used to release drugs in the body, in a controlled manner.
  • Control of timing and target.




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• Conventional Drug Delivery Systems:
  – tablets, capsules, pills, suppositories, creams,
    ointments, liquids, aerosols, and injectables




                   From Chien, Novel Drug Delivery Systems. pg 2.
           Polymeric DDSs
• Polymeric matrix incorporates drug
• Known release rate over prolonged duration
• Release to target (site of action)
• Goal: constant release
• Target concentration in tissue depends on
  tissue absorption, drug kinetics, etc
• Drug protection when in situ (particularly for
  longer release periods)
             DDS types
• Monolithic devices: matrix systems
• Reservoir devices: rate controlling
  membranes
• Degradable systems: polymers degrade
  due to chemical action
DDS types, again




       From Shi, Biomedical
       Devices and their
       Applications, 2004
Diffusion in monolithic and
     reservoir devices




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What happens after delivery?




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Use Fick’s law to design drug release
Rate control
“smart materials”, mechanism of action




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Biodegradable systems
            Figure 7. Drug delivery from (a) bulk-eroding
            and (b) surface-eroding biodegradable systems




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Biodegradable PLA and PEG




                   PLA = poly(lactic) acid
      PLGA (poly lactic-co-glycolic acid)
            and polyorthoester
                         Biodegradable microparticles of 60:40
                         lactide:glycolide PLGA. (Photo courtesy of
                         T. Tice, Southern Research Institute,
                         Birmingham, AL.)


                                Biodegradable microparticle of 75:25
                             lactide:glycolide PLGA after 133 days of
                                                 degradation in water.




Biodegradable polyorthoester rods after (left) 9 and (right) 16 weeks of implantation in rabbits.
(Photos courtesy of H. Heller, Advanced Polymer Systems, Redwood City, CA.)
        Elementary osmotic pump




Pressure-controlled release. Pressure increases due to osmosis.


                  http://www.uweb.engr.washington.edu/research/tutorials/drugdelivery.html
Extra salt layer: two compartment pump
Alza – Duros pump




http://www.alza.com/alza/duros
Two-compartment osmotic
   (commercial) pump
       Diabetes




From Chien, Novel Drug Delivery Systems. Figure 30, pg 35.
Ocusert, pilocarpine to glaucoma
             patients




        From Chien, Novel Drug Delivery Systems. Figure 1, pg 260.
Transdermal delivery (patches)




       Cleary GW, "Transdermal Delivery Systems: A Medical Rationale," in Topical Drug
       Bioavailability, Bioequivalence, and Penetration, Shah VP, and Maibach HI (eds),
       New York, Plenum, pp 17–68, 1993.
                      “Smart
                   materials”
                    designed
                    based on
                external cues




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