Controlled drug release from a spheroidal matrix

Drug transport through a spheroidal matrix was studied using Fick's second law of diffusion in spherical coordinates. The prolate spheroid-shaped geometry was described by a small angular deformation applied at the surface of the body. An infinite series of Legendre polynomials of order two was first used to develop an expression for the solute concentration in the Laplace domain. This method resulted in closed-form expressions for the effective time constant and the cumulative percentage of drug released in terms of critical model parameters. The procedure predicted published solutions very well. More moisture was observed at the center of the body when compared to the focal point. As the aspect ratio increased, the effective time constant decreased. At 0.38 unit time, 98.6% of the loaded drug was released from the device.