The Higuchi Plot
• In 1961 Higuchi developed a mathematical model for the study of the release
of drugs from its matrix.
• For studying the release of water-soluble and poorly soluble drugs from a
variety of matrices, including semisolid and solids.
• Initial drug concentration in the matrix is much higher.
• As the drug is released, the distance for diffusion progressively increases.
• Drug is leached out polymer matrix by the entrance of medium.
• The Equation Of Higuchi model:
Q= [D(2A-Cs)Cs x t]1/2 or
• By differentiating the above equation we get,
• Release of the drug is proportional to the square root of time.
• The Drug release from the granular matrix is given by
Applications of Higuchi Plot
• Higuchi describes the drug release as a diffusion process based on Fick's law,
square root time dependent.
• This model is useful for studying the release of water-soluble and poorly
soluble drugs from a variety of matrices, including solids and semi-solids.
• A simple relationship that described drug release from a polymeric system
equation was derived by Korsmeyer-Peppa in 1983.
• To understand the mechanism of drug release and to compare the release
profile differences among these matrix formulations , the percent drug
released time versus time were fitted using this equation:
• The n value characterizes different releases from matrix and specify release
mechanisms as shown below:
Release Exponent (n) Drug transport mechanism
0.5 Fickian diffusion
0.5<n=0.89 Non Fickian transport
0.89 Case II transport
Higher than 0.89 Super case II transport
• To study release kinetic data obtained plotted as log cumulative % drug
release versus time.
Applications of Peppas Plot
• This equation has been used for the linearization of release data from several
formulations of microcapsules or microspheres.
• Use to analyze the release of pharmaceutical polymeric dosage form.
• When the release mechanism is not known or when more than one type of
release phenomena could be involved.
• To study the modified release dosage form and release phenomenon of drugs.