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The following message was posted to: PharmPK
Dear all,
How to calculate Korsemeyer peppas constant and n value for the data
of in vitro drug release from formulation, and what is its importance
to interpret the in vitro dissolution data and does it indicate the
mechanism of drug release from the formulation.
Regards
Ketan
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The following message was posted to: PharmPK
Dear Ketan,
Assuming that the polymeric formulation is non-swellable and
non-degradable, the Peppas equation refers to mechanisms of
relesae as Fickian and non-Fickian. A simple equation
relation an exponential time factor (n) to the cumulative
amount of loaded drug released was originally suggested by
Peppas at al.
Here is the original but very useful reference:
Pharm Acta Helv. 1985;60(4):110-1.
Analysis of Fickian and non-Fickian drug release from
polymers.
Peppas NA.
Hope this helps.
Murad
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The following message was posted to: PharmPK
Q=b + Kp*t**n
In this equation Q represents the percent of drug
released at time t ; Kp is constant incorporating
structural and geometric characteristics of the
release device, and n is the release exponent
indicative of the mechanism of release. When n
approaches 0.5, a Fickian /diffusion-controlled
release is implied, where 0.5 < n < 1.0 non-Fickian
transport and n=1 or near 1 for zero-order ; b
corresponds to the intercept accommodating the burst
effect..
You can obtain the parameters by non linear regression
of the amounts dissolved (percent released) versus
time
Korsmeyer R.W., Gurney R., Doelker E., Buri P., Peppas
N.A. (1983) Mechanisms of solute release from porous
hydrophilic polymers. J. Pharm. Sci., 15: 25-35.
regards
marival
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Hi,
1. the best method is to fit the dissolution equation in WNL as it,
%Dis=k*(time**n); constrain n between 0.3 and 1.2 with initial 0.5
2. for better initial estimate of param, do log liniarisation of
equation, exp-intercept is k and slope is n
3. maybe you have to consider some alternatives for data analysis, in
many instances you will obtain a better fit using a mixed order kinetic
release mechanism (0 order + 1st order, different lag times)
4. with either method, usually you can obtain a good fit for %dis up to
75-85%
regards,
laurian vlase
Vlase Laurian
MD, PhD, Pharm. Chem.
Teaching Assistant
Dept. of Pharmaceutical Technology and Biopharmaceutics
Faculty of Pharmacy
University of Medicine and Pharmacy "Iuliu Hatieganu"
13, Emil Isac
Cluj-Napoca, Cluj 400023, Romania
email:vlaselaur.-at-.yahoo.com
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The following message was posted to: PharmPK
Dear Vlase, Regarding fitting dissolution and Korsemeyer peppas constant
Yes, Vlase, I have seen good fits up to about 80% as you suggest. I
have looked for a reference to justify not going closer to 100%. Do
you know of a reference?
Regards,
Frank
Frank Bales
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Hi,
you cannot obtain a fit up to 100% with Peppas or Higuchi.
If you look at the formula, for t is inf you get %dis is inf, which
is not possible.
Besides, if you consider Peppas relation on all the diss process,
this process will stop suddenly at 100%, which is also not realistic.
you can try a 1st order release model for the rest of 15-20% diss and
let WNL to calculate also the time for switching from Peppas to 1st
order process. (you will have two more param on final model, time of
switching and k1)
regards,
laurian
Vlase Laurian
MD, PhD, Pharm. Chem.
Teaching Assistant
Dept. of Pharmaceutical Technology and Biopharmaceutics
Faculty of Pharmacy
University of Medicine and Pharmacy "Iuliu Hatieganu"
13, Emil Isac
Cluj-Napoca, Cluj 400023, Romania
email:vlaselaur.-a-.yahoo.com
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