PharmPK Discussion - Weibull function to fit dissolution data

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On 3 Dec 2004 at 17:16:29, Sumithra Gopal (Sumithra.Gopal.-at-.biovail-btl.com) sent the message


The following message was posted to: PharmPK

I am trying to fit my in-vitro dissolution data to the Weibull
Equation.  Is
it possible to use WinNonlin.  If yes, how do I?
If not, is there any other method.

Also, I have come across different Weibull equations (at least three)
and
I'm not sure which one I should use.

Any suggestions will be appreciated

Thanks,

Sumithra

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On 3 Dec 2004 at 15:16:48, "Walt Woltosz" (walt.-at-.simulations-plus.com) sent the message


The following message was posted to: PharmPK

The following message was posted to: PharmPK by Sumithra Gopal:

"I am trying to fit my in-vitro dissolution data to the Weibull
Equation.  Is it possible to use WinNonlin.  If yes, how do I?
If not, is there any other method.

Also, I have come across different Weibull equations (at least three)
and I'm not sure which one I should use."

GastroPlus provides both Weibull and tabulated options for
released/dissolution.

The Weibull function we use is:

	% released = 100 * (1 - exp[ - (t-Tlag)^b / A] )

		where T = time lag, h
			A = time scale, h
			b = shaping parameter

Walt Woltosz
Chairman & CEO
Simulations Plus, Inc. (AMEX: SLP)
1220 W. Avenue J
Lancaster, CA  93534-2902
U.S.A.
http://www.simulations-plus.com
Phone: (661) 723-7723
FAX:   (661) 723-5524
E-mail: walt.-a-.simulations-plus.com

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On 3 Dec 2004 at 18:00:04, "Michael B. Bolger" (bolger.-a-.simulations-plus.com) sent the message


The following message was posted to: PharmPK

The following URL leads to a simple Excel spreadsheet for fitting a
Weibull
to in vitro dissolution data.  Use the Excel addin optimizer (under
Tools/Solver) to fit any or all of the three Weibull parameters.

ftp://labsoft.hsc.usc.edu/pub/Absorption/WeibullFunctionExport.xls

Mike

*  Michael B. Bolger, Ph.D.
*  Director of Life Sciences and Founding Scientist
*  Phone: 707-769-1895 or (661) 723-7723 x 254
*  FAX:   (661) 723-5524
*  Simulations Plus, Inc.
*  1220 West Avenue J
*  Lancaster, CA  93534-2902
*  U.S.A.
*  http://www.simulations-plus.com (AMEX: SLP)
*  bolger.at.simulations-plus.com

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On 3 Dec 2004 at 22:10:40, Vlase Laurian (vlaselaur.-a-.yahoo.com) sent the message


The following message was posted to: PharmPK

Hi,
please find the code for Weibull model in WNL
note that if you want to use empirical models for analysis of
dissolution data, try also Logistic, Hill, Morgan, Richards, Hopfenberg
(is a mechanistic but in some instances can be used as empirical).
Regards,
vlase laurian

Model 1
COMMANDS
NFUNCTIONS 1
NPARAMETERS 3
PNAMES  'Td','beta','tlag'
initial   67,   0.8,    5
lower      5,   0,    0
upper      125,  2,  10
reweigth -1
END
TEMPORARY
t=x
END
FUNCTION 1
if t<= tlag then
F=0
else
expon= -((t-tlag)/Td)**beta
F= 100*(1-dexp(expon))
endif
END
EOM

Vlase Laurian
Dept. of Pharmaceutical Technology and Biopharmaceutics
Faculty of Pharmacy
University of Medicine and Pharmacy "Iuliu Hatieganu"
13, Emil Isac
Cluj-Napoca, Cluj 3400, Romania
vlaselaur.-at-.yahoo.com
online on Yahoo Messenger

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