Hello!
I am investigating permeability of a drug trough silicone membrane. I plotted a permeation profile graph
x axis: time [h];
y axis: cumulative amount of drug [ug/cm2]
Does anyone know how from this point how do I calculate steady state flux [ug/cm2/h]?
Dear Mira,
The first step you should do is following the FDA Guideline for nonsterile semisolid (attached below). You should take an aliquot of donor compartement fluid at different interval time, at least 5 samplIng time before the steady state. After sampling all of the aliquote, follow the formula in the article (attached below) in order to get the cumulative penetration each sampling time. I hope theses articles could help you to calculate the drug permeation and flux.
http://www.sciencedirect.com/science/article/pii/S0378517305008434
www.fda.gov › Guidances › UCM070930
The instantaneous flux at time t is the slope of the line of your cumulative at that point. You could fit a curve and differentiate, or simply use discrete intervals: get the slope between successive pairs of points and calculate the slope (y2-y1)/(x2-x1) and plot the result against time. As this value will be an average between the two time points, you may want to plot it against the mean time (x2-x1)/2. Regards. Deon
Dear Mira,
Use Nernst–Planck equation to calculate flux of the drug permeability.
Refer site given below.
http://www.pharmpress.com/files/docs/MolBiopharmaceutics_sample.pdf
(equation no. 3.2.11 and 3.2.12 can be useful for you)
Ashish
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