Release from bioerodible microparticles

When Fickian diffusion in normal Euclidean space is justified, further verification can be obtained from the analysis of 60% of the release data using the power law in accord with the values of the exponent quoted in Table 4.1. Special attention is given below for the values of b in the range 0.75-1.0, which indicate a combined release mechanism. Simulated pseudodata were used to substantiate this argument assuming that the release obeys exclusively Fickian diffusion up to time t = 90 (arbitrary units), while for I, 90 a Case II transport starts to operate too this scenario can be modeled using 

the following equation was used to simulate concurrent release mechanisms of Fickian diffusion and Case II transport throughout the release process  

In bioerodible drug delivery systems various physicochemical processes take place upon contact of the device with the release medium. Apart from the classical physical mass transport phenomena (water imbibition into the system, drug dissolution, diffusion of the drug, creation of water-filled pores) chemical reactions (polymer degradation, breakdown of the polymeric structure once the system becomes unstable upon erosion) occur during drug release. 

The mathematical model developed by Siepmann et al. [91] utilizes Monte Carlo techniques to simulate both the degradation of the ester bonds of the 

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Faisant, N., Saipmann, J., et al. The effect of gamma-irradiation on drug release from bioerodible microparticles A quantitative treatment. Int. J. Pharm. 242 281—284, 2002. 

Siepmann, J., Faisant, N., and Benoit, J., A new mathematical model quantifying drug release from bioerodible microparticles using Monte Carlo simulations, Pharmaceutical Research, Vol. 19, No. 12, 2002, pp.1885-1893. 

Faisant N, Siepmann J, Richard J, et al. Mathematical modeling of drug release from bioerodible microparticles effect of gamma-irradiation. Eur J Pharm Biopharm 2003 56 271-279. 

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