# Re: RE: Dataset coding for baseline endogenous substance

From: Paolo Denti <paolo.denti>
Date: Wed, 27 May 2015 05:52:21 +0000

for actual code examples and methods to introduce error or estimate you bas=
eline, I would suggest looking into this paper.

C. Dansirikul, H. E. Silber, and M. O. Karlsson, “Approaches to handling =
pharmacodynamic baseline responses,” J. Pharmacokinet. Pharmacodyn., vol.=
35, no. 3, pp. 269–283, Jun. 2008.

The appendix includes code and dataset examples, so it should be of help.

Regards,
Paolo

On 2015/05/27 01:01, Denney, William S. wrote:

Generally, you will just include the baseline measurement as time=0 and t=
hen reference all other times from that time. So, if your baseline value w=
as drawn at 8AM on day 1 while the first dose was at 10AM, just set the bas=
eline time as 0 and the first dose time as 2 (also assuming that your time =
is in hours). If baseline is taken far before the next time, the only impo=
rtant part is that you want the time between baseline and the next measurem=
ent to be more than ~5-fold the auto-correlation time of your system.

From there, you will estimate your A_0 values as you have seen other places=
. A general note that is not always covered in other discussions of endoge=
nous substance PK: You want to make sure that your equations work so that =
A_0 is at steady state (usually). Often, you will not directly set A_0, bu=
t you will solve the equations for A_0 being steady-state and set it to the=

Thanks,

Bill

From: owner-nmusers
ilto:owner-nmusers
Sent: Tuesday, May 26, 2015 6:02 PM
To: nmusers
Subject: [NMusers] Dataset coding for baseline endogenous substance

I am modeling a drug that is also an endogenous substance.

I have found quite a bit of information on modeling practices with endogeno=
us substances, but nothing on how to incorporate the baseline endogenous su=
bstance value (DV) into the dataset.

The data is from clinical use, and the baseline values are not drawn at exa=
ctly the same times prior to drug administration.

Any assistance would be appreciated! Thank you in advance…

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--
------------------------------------------------
Paolo Denti, PhD
Pharmacometrics Group
Division of Clinical Pharmacology
Department of Medicine
University of Cape Town

K45 Old Main Building
Groote Schuur Hospital
Observatory, Cape Town
7925 South Africa
phone: +27 21 404 7719
fax: +27 21 448 1989
email: paolo.denti
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Received on Wed May 27 2015 - 01:52:21 EDT

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