# Re: [FORGED] [NMusers] Modelling IV and IP simultaneously

From: Nick Holford <n.holford_at_auckland.ac.nz>
Date: Mon, 24 Apr 2017 18:21:47 +0200

Fanny,

It is a common misconception (for many decades) that CMT has to be used
to identify the prediction. CMT is best used to identify the compartment
you want to put the AMT into. In some simple cases it can be used to
identify the prediction.
The more general solution is to add a data item to your data file which
indicates the type of prediction you want to return. I use the name DVID
for this data item.

e.g.

ID TIME DVID DV
1 0 0 . ; dose record
1 10 1 10 ; single compartment amount
1 10 2 100 ; sum of several compartments

\$INPUT ID TIME DVID DV

\$ERROR
IF (DVID.LE.1) THEN
Y=A(2)+EPS(1)
ENDIF
IF (DVID.EQ.2) THEN
Y=A(6)+A(7)+A(8) + EPS(2)
ENDIF

Best wishes

Nick

On 24-Apr-17 17:26, Fanny Gallais wrote:
>
> Dear NMusers,
>
> I'm having trouble writing the code for my model. I have IV and IP
> administrations data, that I would like to model simultaneously. We
> found out that IP was best modeled by a first order absorption, using
> an input compartment (DADT(1)=-KA*A(1)). At first, we used a CMT
> column in the dataset to indicate for each dosing event if it is IV or
> IP. But then, as we made the model more complicated, we realized that
> we couldn't use a CMT column. We study the parent compound, as well as
> its metabolite at the same time but the problem is we cannot put a
> compartment number for the metabolite's observations. This is because,
> given the model structure, the prediction for the metabolite
> concentrations is a sum of 3 concentrations in 3 different
> compartments (e.g. IPRED=A(6)+A(7)+A(8)). So we think that putting a
> compartment number for the observation would be confusing for NONMEM.
> What do you think? Do you see how we could model IV and IP
> simultaneously, without using the CMT column ? or any other solution?
>
> Thank you for your help
>
> Fanny Gallais

--
Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology, Bldg 503 Room 302A
University of Auckland,85 Park Rd,Private Bag 92019,Auckland,New Zealand
office:+64(9)923-6730 mobile:NZ+64(21)46 23 53 FR+33(6)62 32 46 72
email: n.holford_at_auckland.ac.nz
http://holford.fmhs.auckland.ac.nz/
http://orcid.org/0000-0002-4031-2514