For slab geometry in Korsmeyer-Peppas, what does n ≈ 0.5 indicate?

• A. Fickian diffusion
• B. Case-II transport
• C. Anomalous (mixed) transport
• D. Zero-order release

Answer: (A)

In the Korsmeyer-Peppas model for a planar (slab) geometry, the release exponent n tells you what mechanism mainly governs the drug's escape. When n is about 0.5, the process is controlled by Fickian diffusion—drug molecules diffuse through the polymer matrix and the rate is governed by this diffusion, with little to no contribution from relaxation or swelling of the polymer. If n were near 1, it would indicate Case-II transport (polymer relaxation-driven, often showing zero-order release), and values between 0.5 and 1 indicate anomalous transport (a mix of diffusion and relaxation effects). The geometry sets the exact threshold, so for a slab, n ≈ 0.5 corresponds to Fickian diffusion.