Dear All,
I am using PDxPop4-NONMEM.
When I am using ADVAN 5/9 in my control file I come across this sentence
after $PK line (S1=1 ;modify as req'd for scale parameter &/or dose-obs unit
differences). I didnt understand this. I went through the PDxPOP 4 Manual
(Page #107/108 ) which is written as follows.
The control file is complete with one exception. The correct compartment for
scaling the observation, S2 in
this case, was selected but the parameter for scaling, for example V, cannot
be known apriori and must be
added by typing it on the S2 line (e.g. S2=V ;). Also, any correction for
differences in units between the dose
and the observation (e.g. AMT in mg and DV in ug/L) must also be added
manually to the control stream
(S2=V/1000). Make any required changes to the control file, save, and close
the file. The new file will now
be found under “Control Streams Selected” on the Model/Run Tab and the model
can be run.
I didnt get their point yet. My model isnt working if I ignore this sentence
and I think it could be probably because of the above reason.
I appreciate your suggestions.
Thank you very much.
ADVAN5/9 ISSUES - PDxPop4-NONMEM Users
Shankar,
This is an excellent question, and I agree that the text you provided from the
manual is not very clear. Similarly, the NONMEM help files are somewhat
ambiguous on this topic. The scale parameter (S2) converts the amount of drug
in a compartment to the concentration of drug in the compartment. This
conversion is required for your model to fit the observed concentration data.
You can read a full explanation on my blog at http://wp.me/p1fZzZ-4O.
I hope this helps you understand the scale parameter. Good luck modeling!
Best regards,
Nathan Teuscher
www.learnpkpd.com
blog.learnpkpd.com
Quoted reply history
On Jan 26, 2011, at 2:56 PM, Shankar Lanke wrote:
> Dear All,
>
> I am using PDxPop4-NONMEM.
>
> When I am using ADVAN 5/9 in my control file I come across this sentence
> after $PK line (S1=1 ;modify as req'd for scale parameter &/or dose-obs unit
> differences). I didnt understand this. I went through the PDxPOP 4 Manual
> (Page #107/108 ) which is written as follows.
> The control file is complete with one exception. The correct compartment for
> scaling the observation, S2 in
> this case, was selected but the parameter for scaling, for example V, cannot
> be known apriori and must be
> added by typing it on the S2 line (e.g. S2=V ;). Also, any correction for
> differences in units between the dose
> and the observation (e.g. AMT in mg and DV in ug/L) must also be added
> manually to the control stream
> (S2=V/1000). Make any required changes to the control file, save, and close
> the file. The new file will now
> be found under “Control Streams Selected” on the Model/Run Tab and the model
> can be run.
>
> I didnt get their point yet. My model isnt working if I ignore this sentence
> and I think it could be probably because of the above reason.
>
> I appreciate your suggestions.
>
> Thank you very much.