Hello All
I am trying to fit two data sets with the same model.I am using a simple 2 C model (linear kinetics)
One data set belongs to single dose and the other has multiple dosing ( for which i have C troughs only). Doses are same for the single and multiple dose
Phoenix is fitting a straight line to the multiple dose values
I was wondering if there is a workaround for this?
Thank you
Hi Vaishnavi, without seeing the data it’s hard to see where the problem lies.
how does your initial estimates tab look, for instance if you see this data from the classic phenobarital modelling exercise, the multiple dose curves are described with only a few supporting observation points.
Are you sure that it is not just an artefact of only looking at the default plots that show predicted concentrations at observed times only?
Have you tried asking for a table output with points over a multiple dose day and then plotted that?
If you still have no luck then I think you’ll have to attach the project for others to review.
Simon.
Dear Vaishnavi
I am pretty sure I know what you did and I am attaching a project I made that should help you.
Apparently you do not have accumulation and you did not ask for a table with many time points as output. If you do not ask for a table with many times points to cover the full range and no accumulation , I guess you will see something like a straight line.
The project attached explains everything.
I fit combined single and multiple data sets and fit those.
However I asked for a table as output to make sure I will see the predictions across the whole range and not only at trough levels.
Everything works fine and I do not see any issue here.
Let me know if the project attached helps.
best
Serge
single_and_multiple_dose.phxproj (3.51 MB)
I made a small cosmetic edit to the plots to illustrate better Serge’s point.
single_and_multiple_dose.phxproj (6.07 MB)Dear Serge ,
I have Phoenix Version 6.3.0 and your file is 6.4.0. Is there any way you can send this in an older version?
I can see your data file but not your model structure
Thank you so much
Vaishnavi
Can you try this one?
Let me know.
Please upgrade your version. This is really too old.
'Best
Serge
Yes particularly if you are using NLME a lot you should try to keep more current; Phoenix 7 was released earlier this month;
https://www.certara.com/software/pkpd-modeling-and-simulation/phoenix-7-0/
and there will be a webinar on the 14th Sept. at 11am EDT | 4pm GMT | 5pm CEST
Simon
Thank you Simon and Serge !
yes this works.
And yes I am working on getting a newer version 
Vaishnavi
