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RE: Simultaneous vs sequential for modeling parent AND metabolites in pop PK

From: Wang, Yaning <>
Date: Wed, 10 Dec 2008 17:34:21 -0500


When FDA sends out a request, there should be a rationale for it. If it
is not clear enough, the sponsors should ask for clarification. If after
clarification, the sponsors felt the rationale is not scientific, then
the sponsors should not hesitate to appeal such requests. The sponsors
can appeal to the Director of Pharmacometrics at FDA if necessary.


Yaning Wang, Ph.D.
Team Leader, Pharmacometrics
Office of Clinical Pharmacology
Office of Translational Science
Center for Drug Evaluation and Research
U.S. Food and Drug Administration
Phone: 301-796-1624

"The contents of this message are mine personally and do not necessarily
reflect any position of the Government or the Food and Drug

-----Original Message-----
From: owner-nmusers
On Behalf Of Hussein, Ziad
Sent: Tuesday, December 09, 2008 11:38 AM
To: Xiao, Alan; nmusers
Subject: RE: [NMusers] Simultaneous vs sequential for modeling parent
AND metabolites in pop PK

Hi Alan,

I just had a very recent experience few weeks ago for a sequential PopPK
for parent and metabolite that was submitted to the FDA and they came
back and asked for simultaneous modelling.

Whether this is scientific or not the FDA view should be taken into

Kind regards,

-----Original Message-----
From: owner-nmusers
On Behalf Of Xiao, Alan
Sent: 09 December 2008 16:02
To: nmusers
Subject: [NMusers] Simultaneous vs sequential for modeling parent AND
metabolites in pop PK

Dear All,

I know this is an old topic but would like to see the statistics.

When you have to develop a pop PK model for both parent and active
metabolites, which approach do you prefer or have you used most:
simultaneous or sequential? Which way do you think is more scientific? I
heard comments saying that the simultaneous approach is not scientific.


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Received on Wed Dec 10 2008 - 17:34:21 EST

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