Table 1. Release Kinetic Models and Their Corresponding Mathematical Equations^a.

release kinetic model	mathematical equation	remarks
Higuchi38		Mt—amount of drug released at time t
		M∞—total amount of drug released along the process
Ritger–Peppas39		kH—Higuchi kinetic constant
		kP—Ritger-Peppas kinetic constant
		n—release exponent
Berens–Hopfenberg40		⌀F—fractional diffusion contribution
		⌀R—fractional chain relaxation contribution
	kR = 1/τ	kF—diffusion constant
		kR— first-order chain relaxation constant
		D—diffusion coefficient
		d—film thickness
		τ—characteristic chain relaxation time

^aThe value of the release exponent in the Ritger–Peppas model provides information regarding the drug release mechanism: n = 0.5—Fickian, or diffusion-controlled release; 0.5 < n < 1.0—anomalous, or both diffusion- and polymer relaxation-controlled mechanism; n = 1.0—non-Fickian, or relaxation-controlled release.³⁹