Quantifying diffusion-controlled drug release from spherical devices using Monte Carlo simulations

We numerically calculate drug release profiles from simple spherical devices using Monte Carlo simulations, when diffusion is the dominant release mechanism. Release curves are accurately described by the stretched exponential function, also known as the Weibull function. The dependence of the two stretched exponential parameters on the size of the spherical device and the drug diffusion coefficient is investigated and simple analytical relations are provided. Release kinetics does not depend on the initial drug concentration. The obtained results are compared with predictions derived from the analytical solution of Fick's second law of diffusion. (C) 2012 Elsevier B.V. All rights reserved.