VIEWS: 23 PAGES: 22 POSTED ON: 4/1/2012
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. http://www.devicelink.com/mpb/archive/97/11/9711b34b.jpg • 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 http://www.devicelink.com/mpb/archive/97/11/003.html What happens after delivery? http://www.devicelink.com/mpb/archive/97/11/003.html Use Fick’s law to design drug release Rate control “smart materials”, mechanism of action http://www.devicelink.com/mpb/archive/97/11/003.html Biodegradable systems Figure 7. Drug delivery from (a) bulk-eroding and (b) surface-eroding biodegradable systems http://www.devicelink.com/mpb/archive/97/11/003.html 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 http://www.devicelink.com/mpb/archive/97/11/003.html
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