A simple equation for description of solute release II. Fickian and anomalous release from swellable devices

The previously (Ritger and Peppas, 1987) introduced exponential relation Mt/M∞ = ktn may be used to describe the Fickian and non-Fickian release behavior of swelling-controlled release systems which swell to a moderate equilibrium degree of swelling and are prepared by incorporation of a drug in a hydrophilic, initially glassy polymer. Again the diffusional exponent, n, is an important indicator of the mechanism of transport of a drug through the polymer. Analysis is presented for solute release from sheets, cylinders, spheres and polydisperse samples.