Back to the Top
Hi!
Is there any easy was to implement a multiple dosing regimen (e.g. 500
mg
tid for 7 days) in Winnonlin? An example of a written code (any multiple
dosing regimen) would be appreciated.
T. Gordi
Back to the Top
Dear T. Gordi:
You might try the USC*PACK programs. They handle multiple
dosing regimens all the time, as they are designed to study and model
the behavior of drugs especially in acutely ill, unstable, patients.
The quality of the analyses is at least as good. You might go to our
web site
ww.lapk.org
and click on new advances in PK/PD modeling, and see a thoughtful
comparison on parametric methods using the FOCE approximation and the
nonparametric methods, with respect to consistency, efficiency (getting
the most information, the most precise parameter estimates, out of your
data), etc.
Very best regards,
Roger Jelliffe
Roger W. Jelliffe, M.D. Professor of Medicine,
Division of Geriatric Medicine,
Laboratory of Applied Pharmacokinetics,
USC Keck School of Medicine
2250 Alcazar St, Los Angeles CA 90033, USA
email = jelliffe.-a-.usc.edu
Our web site = http://www.lapk.org
Back to the Top
At 06:57 AM 10/17/02, T.Gordi wrote:
> Is there any easy was to implement a multiple dosing regimen (e.g. 500
> mg
> tid for 7 days) in Winnonlin? An example of a written code (any
> multiple
> dosing regimen) would be appreciated.
I don't know about WinNonlin, but it's incredibly simple in
GastroPlus(tm). In fact, you can easily set up "Mixed Multiple Doses",
such as an IV bolus at time zero, with an IV infusion also starting at
time zero, with an oral solution at 8 hours, then an oral tablet at 24
hours, etc. - in other words, any combination of dosage forms
administered at any time. You can also easily fit an
absorption/pharmacokinetic model to observed data produced from any
such combination of doses.
Walt Woltosz
Chairman & CEO
Simulations Plus, Inc. (SIMU)
1220 W. Avenue J
Lancaster, CA 93534-2902
U.S.A.
http://www.simulations-plus.com
E-mail: walt.at.simulations-plus.com
Back to the Top
T. Gordi....
WinNonlin can easily and effectively implement a multiple dosing
regimen (500mg tid for 7 days) as you requested. There are a couple of
different approaches you can take depending on the use of a user
defined or library model. The approach below describes the steps
needed to construct a user define model using a multiple dose regimen.
The easiest way to accommodate a multiple dose regimen in a
user-written model is to use a ASCII version of one of the library
models as a starting point. When you go through the PK/PD/NCA Analysis
Wizard, select the ASCII rather than the Compiled version of the model.
Use this model (ASCII) as a template for your own model, making sure to
retain the programmed loops. Superposition is used to implement
multiple dosing. Here is some annotated example code for the FUNCTION
block.
func1
j=1
ndose=con(1)
do i = 1 to ndose
j=j+2
if x <= con(j) then goto red
endif
next
(This loop counts the number of doses administered up to time x)
red:
ndose = i-1
(This label begins the superposition section by initializing the
variables sum and j)
sum=0
j=1
do i = 1 to ndose
j=j+2
t=x - con(j)
d=con(j-1)
coef= d*k01/(v*(k01-k10))
amt=coef*(exp(-k10*t)-exp(-k01*t))
sum=sum + amt
next
(This loop performs the superposition by summing the contribution of
each dose to the observation at time=x and includes the user specified
PK model)
f=sum
end
For further technical support regarding WinNonlin or any of our other
products please feel free to contact our support inbox at: http:
//www.pharsight.com/support/index.php
Thanks,
Jeff D. Fischer
Pharsight
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)