Results and Discussion (Part 3)

1
Results and Discussion (Part 3)

• Dan Duffield
• Rick Pelletier
• 2-14-2006

2
Previous Equations

• Equations 1 through 9 have several limitations
  and do not apply-
• At low loadings (lt15), pore space may not be
  interconnected.
• For macromolecules whose solubility is less than
  250 mg/mL.

3
F factor and Porosity

• The relation between the F factor and the
  porosity in Equation 9 is empirical.
• This may not be useful outside its known range of
  validity (0.15lt e lt0.35)

4
Simplification of Diffusion Equations

• The diffusion equations used in this study are
  simplifications of more complex processes.
• The factor F must take into account matrix pore
  geometric factors contributing to decreases in
  diffusion rates such as
• Pore Tortuosity
• Dead-end Pores
• Constrictions between pores
• Understanding of these factors will be important
  in further developing macromolecular delivery
  systems.

5
Release Rates

• In vitro and in vivo release rates of
  macromolecules from identical EVAc slabs are
  identical.
• Constant release rates are attainable from EVAc
  systems with appropriate geometric design.

6
Use of Present Study

• Helps to explain why macromolecules can slowly
  permeate through normally impermeable polymers.
• Data should be useful in the design of release
  vehicles for-
• Polypeptides
• Polysaccharides
• Bioactive agents

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Use of Present Study (cont.)

• These substances often possess very short in vivo
  life times and conventional dosage forms can not
  be used to deliver these drugs.
• The methodology developed here may be of value in
  the design of systems for long-term delivery of
  macromolecules.

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Questions

• ?