Controlled Drug Release from Polymeric Matrices Involving Moving Boundaries

  • P. I. Lee


The diffusional release of a dispersed or dissolved drug from a polymeric matrix generally involves the presence of a moving diffusional front separating the undissolved core and the partially extracted region. In the case of an erodible or swellable polymer matrix, the release kinetics is further complicated by the presence of a second moving boundary, namely the eroding or swelling polymer front. The mathematical descriptions of such mass transfer problems involving moving boundaries are known as moving boundary problems, free boundary problems, or simply Stefan problems. Except for some special cases, the presence of a moving boundary introduces a nonlinearity so that only a few exact solutions are known.1–3 In addition to numerical schemes, various approximate analytical techniques have been applied to moving boundary problems developed in other areas such as freezing and melting with varying degree of success.2,3 However, only very simple pseudosteady state approximations have been used to analyze the release of a dispersed drug from a polymeric matrix.4,5


Drug Release Control Drug Release Move Boundary Problem Fractional Release Diffusion Front 
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Copyright information

© Springer Science+Business Media New York 1981

Authors and Affiliations

  • P. I. Lee
    • 1
  1. 1.Central ResearchCIBA-GEIGY CorporationArdsleyUSA

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