ADT Exam 1

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ADT Exam 1
2011-10-10 20:57:54
Ocular Drug Delivery

Ocular Drug Delivery
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  1. Rate determining layer of the eye
    corneal epithelium
  2. Retinal pigmented epithelium
    • acts like BBB
    • site of DM retinopathy begining
  3. Barriers to ocular drug delivery
    • corneal epithelium
    • tearing/blinking
    • tight junctions
    • efflux proteins (PGP and MRP)
    • blood aqueous barrier (ciliary epithelium)
    • Blood retinal barrier
  4. PGP on the ____ side of the RPE result in limited absorption from the blood.
    basolateral side
  5. Routes of drug delivery to the eye
    • topical
    • intravitreal
    • sub-tenon
    • subconjunctival
    • periocular
    • retrobulbar
  6. Topical drug delivery
    • 90% drug loss due to tears, systemic absorption and blinking reflex
    • drug absorbed into aqueous humor
  7. 3 methods of sub conjunctival delivery
    • direct penetration through tissue to vitreous
    • drug abs into aqueous humor then into vitreous
    • drug abs into general circulation then into vitreous
  8. advantages of subconjunctival administration
    • sustained drug levels in vitreous chamber
    • non invasive
    • higher drug level achevied vs. systemic
    • can accomidate 500 microliters
  9. Periocular injections
    • given in tenon's capsule or retrobulbar
    • drug is placed near sclera
    • sclera is nto a major barrier to diffusion
    • drug levels observed in 20-30 min
  10. ocular anesthesia
    delivered sub-tenon
  11. GCV vitreal implant
    • delivers drug over 6 months
    • must replace every 6 mo
    • associated with endophthalmitis
  12. Implants made from poly lactide/glycolide polymers
    • release drug over 5 to 6 mo and do not need to be replaced
    • put in limbus junction between cornea and conjunctival space
  13. PLGA microspheres
    deliver drugs over 60-90 days
  14. can result in depot formation at the site of injection and result in controlled drug release
  15. Dendrimers
    • branches around a central core
    • gene delivery to reduce corneal transplant rejection
  16. poly amidoamine dendrimers
    allow for more resonance time on the eye
  17. Collagen shields
    • disposable short term therapeutic bandage lense for cornea
    • delivery of therapeutic agents
  18. Iontophoresis
    • use of charge over small time period to drive ions across the membrane
    • used for ionic drugs
    • 3-12xhigher concentrations acheived
  19. Triblock co polymer of PLGA-PEG-PLGA
    • temperature sensitive
    • biocompatible
    • bidegradable
    • turns to gel in eye
    • delivers drug over 3-4 weeks