- On 19 Jul 2005 at 13:23:30, "Ketan Maheshbhai Ranch" (ketan.ranch.-a-.ranbaxy.com) sent the message

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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 - On 19 Jul 2005 at 15:44:35, "MURAD R. MELHEM" (melhemmr.at.email.uc.edu) sent the message

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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 - On 19 Jul 2005 at 13:09:38, marival bermejo (bibilina.aaa.yahoo.com) sent the message

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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 - On 19 Jul 2005 at 13:12:39, Vlase Laurian (vlaselaur.-at-.yahoo.com) sent the message

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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 - On 20 Jul 2005 at 10:50:46, "Frank Bales" (frankbales.at.msn.com) sent the message

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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 - On 23 Jul 2005 at 01:54:08, Vlase Laurian (vlaselaur.-a-.yahoo.com) sent the message

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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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