RE: Endogenous material - C0 is not eq zero
Dear Istvan,
If you assume the production of the endogenous compound is zero-order process
and, at baseline, your system is at steady-state, then you may want to try a
code like what I paste below for one comp IV model.
$PK
BSL = THETA(1) * ETA(1) ;C0 in conc units
CL = THETA(2) * ETA(2)
KEND = BSL*CL
V = THETA(3) * ETA(3)
KEL = CL/V
$DES
DADT(1) = KEND - KEL*A(1)
As far as the assumptions hold, the approach that "is not so good for you"
should provide very similar results than the one just mentioned above for
linear models, such one comp model. For non-linear models, such target mediated
disposition model, the approach suggested above should work better.
Hope it helps,
Juanjo.
Quoted reply history
From: [email protected] [mailto:[email protected]] On
Behalf Of Németh István (FGYFK)
Sent: lunes, 02 de mayo de 2011 7:39
To: '[email protected]'
Subject: [NMusers] Endogenous material - C0 is not eq zero
Dear Users!
I tried to describe the PK of an endogenous material. I started from the
example in UG VIII but after I realize that this method is not so good for me,
because the amount measured in the central compartment is not the object of the
DADTs. Instead of, the dadt describes a system that adjust the amount in the
compartment against the so called base line level, therefore A(1) can be
negative!!! Is there any method that treats situation when the C0 is not zero
(I also interested to estimate C0 somehow).
Thanks,
István
István Németh PhD
Biostatistician
Developmental Drug Metabolism & Pharmacokinetics
Pharmacological and Drug Safety Research
Gedeon Richter Plc
Tel: 00 36 1 505 7082
Fax: 00 36 1 889 8526