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RE: Bayesian estimation example

From: Bhattaram, Atul <atul.bhattaram>
Date: Thu, 12 Apr 2007 08:47:12 -0400

Hello Tausif


One of the many ways to analyze the data you have:

1. Understand the structural model in healthy volunteers using the
average concentration-time data using WinNonlin for example.
2. Use these estimates as your initial parameters and run MAXEVAL=0 =
in
NONMEM and see how the predictions are (This will give you some idea
about the data from patients and your starting model).
3. You can fix some of the parameters (for example ka) and estimate
the parameters of interest.

If your drug has long half-life and the samples that you have are drawn
at pre-dose, then you can use a simpler model (Css=F*Dose/(CL*Tau)) =
and
estimate CL.

With data from 200 patients and 2 or 3 samples (depending on when they
were collected), I think you should be able to estimate the parameters
of interest. You don't need any specific control stream for Bayesian
for this purpose. Regular control stream in NONMEM should work for you.

Atul

Venkatesh Atul Bhattaram
Pharmacometrics
US Food and Drug Administration


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


-----Original Message-----
From: owner-nmusers
On Behalf Of Tausif Ahmed
Sent: Thursday, April 12, 2007 7:03 AM
To: nmusers
Subject: RE: [NMusers] Bayesian estimation example


Dear Group members,

I will make my objective more clear- I have a drug X in which I have
information in healthy volunteers with extensive sampling done, single
dose (12-14 samples).

I have data on appx. 100 volunteers at different dose levels from phase
I studies.

We also have a data in 16 patients at one dose only, with extensive
sampling.

Now we have data from 200 patients, with 2-3 blood samples collected
from each patient at different doses.
It is also seen that the PK changes in patients.
What I am interested is that can we use Bayesian estimates, (and I think
posthoc estimate from NONMEM, as Yaning mentions) to determine the
pharmacokinetics (PK) of the whole population from these 2-3 blood
samples collected per patient.
Hope it is more clear.
I have checked at website- (http://www.accp1.org/)as suggested by many
but could not find any control stream on Bayesian. Can the group help me
on this.
I thank the experts for giving their comments on the same.


Regards
Tausif Ahmed Ph.D.
Metabolism and Pharmacokinetics Department

Ranbaxy Research Lab India

-----Original Message-----
From: Wang, Yaning [mailto:yaning.wang

Sent: Wednesday, April 11, 2007 8:30 PM
To: Nick Holford; Tausif Ahmed
Subject: RE: [NMusers] Bayesian estimation example

Nick:
Tausif may be referring to the posthoc estimate from NONMEM (empirical
Bayesian estimate).
Yaning


-----Original Message-----
From: owner-nmusers
On Behalf Of Nick Holford
Sent: Wednesday, April 11, 2007 10:43 AM
To: Tausif Ahmed
Cc: nmusers
Subject: Re: [NMusers] Bayesian estimation example

Tausif,

Why do you want to use Bayesian Estimation? If you have only just
started to use NONMEM then perhaps you have misunderstood the reasons
for using it. It is very rarely needed.

Nick

> Dear Group members,
>

> I have recently started using NONMEM for population analysis.
> I need you help in understanding Bayesian estimation using NONMEM.
> Can any body provide me a sample control stream along with data file
(Excel or csv format) and also explain the output.
> I use Visual NM to run NONMEM version V.
>

> Thanking you in anticipation.
>

> Regards
> Tausif Ahmed Ph.D.
> Metabolism and Pharmacokinetics Department Ranbaxy Research Lab India

--
Nick Holford, Dept Pharmacology & Clinical Pharmacology University of
Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand
email:n.holford
http://www.health.auckland.ac.nz/pharmacology/staff/nholford/



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Received on Thu Apr 12 2007 - 08:47:12 EDT

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