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


									Drug Delivery Systems

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

What happens after delivery?

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

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

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.

Extra salt layer: two compartment pump
Alza – Duros pump
Two-compartment osmotic
   (commercial) pump

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

        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.
                    based on
                external cues

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