Release Fickian diffusional

Fickian diffusional release form a thin polymer film. Equation (4.3) gives the short-time approximation of the fractional drug released from a thin film of thickness S. 

When equation (1) is applied during the early stages of release (fraction released <0.7) to geometries other than slabs (i.e. tablets), the value of the diffusional exponent, , depends on the geometry of the system [8]. In the case of a cylinder, Fickian diffusion is defined by =0.45 and case II by =0.89. The correct values of exponent for different geometries are reported in Table 2. 

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