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The following message was posted to: PharmPK
Dear All,
I should like to implement a model using Pharsight Trial Simulator.
This model includes an EC50 that varies depending on the
concentration and (independently) time after each drug administration
(in order to empirically describe an adaptive mechanism).
With regard to the concentration dependence, I can easily calculate
the EC50 using an expression block.
But, how can I apply the time after drug administration within an
expression? Is there an internal variable that might be used?
Any Ideas?
Best regards,
Dr. David Czock
University Hospital Ulm
Robert-Koch-Str. 8
89081 Ulm
Germany
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The following message was posted to: PharmPK
Dear David,
You may use different approaches here. Perhaps the most straightforward
is to code an action in the formulation block ('Do After Dose') to reset
a state variable. You could also use a dummy compartment/dosing or use
an oscillating function in combination with an event etc. Or even reset
time by means of new periods (but I do not know by heart how that
effects the concentration state).
Best regards,
Jeroen
J. Elassaiss-Schaap
Scientist PK/PD
Organon NV
PO Box 20, 5340 BH Oss, Netherlands
Phone: + 31 412 66 9320
Fax: + 31 412 66 2506
e-mail: jeroen.elassaiss.at.organon.com
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David - You can make things dependent upon dosing events using the
'Events' block. It is under the 'PD' category. 'Events' work best
for episodic occurences. The 'Actions at Times' is another option,
but best suited for single events.
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)