What is the Higuchi equation?
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What is the Higuchi equation?
Simplified Higuchi model describes the release of drugs from insoluble matrix as a square root of time dependent process based on Fickian diffusion Equation. Q = KH t1/ 2. The data obtained were plotted as cumulative percentage drug release versus square root of time.
How is Higuchi constant calculated?
In its simplified (“classical” ) form, the Higuchi equation reads: M t A = 2 C 0 D C s t {\displaystyle {\frac {M_{t}}{A}}={\sqrt {2\ C_{0}\ D\ C_{s}\ t}}} the saturation concentration in the matrix material.
What is fickian and non fickian diffusion?
The main difference between Fickian and Non Fickian Diffusion is the presence or absence of boundaries; there are no boundaries in Fickian diffusion whereas non Fickian diffusion has a sharp boundary separating the highly swollen region from a dry, glassy region.
What is Hixson Crowell cube root law?
The Hixson-Crowell cube root law describes the release from system where there is a change in surface area and diameter of the particles or tablets [15,16]. The applicability of all of these equations was tested in this work. The dissolution data obtained for all formulations at pH.
Which equation is used in the mathematical Tretament of in vitro drug dissolution?
To study the dissolution from a planar heterogeneous matrix system, where the drug concentration in the matrix is lower than its solubility and the release occurs through pores in the matrix, the expression is given by equation: ft = Q = √Dδ/τ (2C- δCs) t ——————–(16) Where, D is the diffusion coefficient …
When N 0.5 What does it signifies in korsmeyer Peppas equation?
The n values of Korsmeyer-Peppas are mostly less than 0.5 suggesting the release mechanism was governed by diffusion. Consuming drug for a long period could give a negative effect to the body.
How is drug release kinetics calculated?
The fundamental principle for evaluation of the kinetics of drug release was offered by Noyes and Whitney in 1897 as the equation (10): dM/dt = KS (Cs с Ct) (1) where M, is the mass transferred with respect to time, t, by dissolution from the solid particle of instanta- neous surface, S, under the effect of the …
Which form of drug shows faster dissolution?
The most usual situation is for the anhydrous form to have a faster dissolution rate than the hydrate. For example, the dissolution rate of theophylline anhydrate was faster than its hydrate form [62]. In certain cases, hydrate form of the drug may show rapid dissolution rate than its anhydrous form.
What is the Noyes Whitney equation used for?
The Noyes-Whitney function is used to represent how the solid material is dissolved into solution, and it is well used in study of drug dynamic.
Which equation gives rate of drug dissolution?
Dissolution rate can be expressed using the Noyes–Whitney equation. In this model, Cs is the saturation concentration of the solute in question in the given solvent.
How do you calculate the n value in korsmeyer Peppas model?
Take “ln” on both sides of the equation. Then your equation would be ln(Mt/Mi) = ln (k) + n*ln (t).
What is Fick’s 1st law of diffusion?
Fick’s law states that the rate of diffusion of a substance across unit area (such as a surface or membrane) is proportional to the concentration gradient.
How do you calculate N in korsmeyer Peppas model?
One is to do the calculations manually Y = log(y) and X = log(x). A plot of Y vs X gives a slope m = n and an intercept b = log(k). The second way is to plot log(y) vs log(x). When you fit a straight line to this plot, the same results are returned for m = n and b = log(k).
How is dissolution rate calculated?
The dissolution rate maps (r) were then calculated by dividing the surface retreat maps (Ah) by the time step (At = i−j) and the molar volume of calcite (Vm = 3.693 × 10−5 m3·mol−1), resulting in maps with the typical mineral dissolution rate units in [mol·m−2·s−1].
What factors affect dissolution rate?
There are three factors that affect the rate of dissolution: (1) the surface area of the solute, (2) the temperature of the solvent, and (3) the amount of agitation that occurs when the solute and the solvent are mixed.
