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Research Article

Analysis of release data in the evaluation of the physical state of progesterone in matrix systems

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Pages 55-65 | Received 25 Nov 1991, Accepted 14 Dec 1991, Published online: 27 Sep 2008
 

Abstract

Ethylene—vinyl acetate microspheres were prepared by an emulsion solvent-evaporation method as sustained delivery carriers of progesterone. Physical state of the drug in the microspheres was affected by drug loading level. As thermal analysis and mathematical release models showed, low payloads of the matrix supported the molecularly dispersed drug. Crystalline drug appeared only as the drug loading level increased. The release process of the crystalline drug produced a porosity increase in the polymeric system; thus, the drug could diffuse through pores and channels. Hence, the porosity of the matrix structure was affected by the payload. This hypothesis could justify the increasing goodness-of-fit of the release data to the square-root model as the drug loading level of the microspheres increased

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