Simultaneous modeling of PK and categorical PD
From: "Hu, Chuanpu"
Subject: [NMusers] Simultaneous modeling of PK and categorical PD
Date: Tue, 2 Apr 2002 10:24:32 -0500
Dear All,
I am trying to model PK and a categorical PD endpoint simultaneously, and
thought I could achieve that by specifying the likelihood for PK and PD.
However I do not see how to make NONMEM accept the normal likelihood. Just
for a start, I simulated a simple 1-compartment population data, and tried
to use ADVAN1 with
$ERROR
Y = 1/THETA(.) * EXP( -( (DV-F)/THETA(.) )**2/2 )
...
$EST MET=1 LAPLACE LIKE MAX=500
and got an error message that I have not seen before:
ERROR IN CLIK WITH INDIVIDUAL 1 ID=0.10000000E+01
CONDITIONAL LIKELIHOOD FOR SOME OBSERVATION ESTIMATED TO BE NEGLIGIBLE
I tried to replace the estimation step with simulation, but NONMEM did not
like it either (I am guessing because there is no EPS(). ).
Can anyone tell me how to specify the continuous portion of the likelihood?
(I plan to specify the PD likelihood according to the logistic regression
example.)
Thanks,
Chuanpu
----------------------------------------------------------------
Chuanpu Hu, Ph.D.
Modeling and Simulation, U.S.
CPDM
GlaxoSmithKline
Tel: 919-483-8205
Fax: 919-483-6380