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Dear members,
I am a beginner in Pharmacokinetics. In WinNonlin-NCA Analysis, I
have come across some PK parameters related to AUC, other than those
(AUClast & AUCinf_obs) which are commonly used to calculate the
extent of bioavailability.
1) AUCall
2) AUCinf_D_obs
3) AUC_%Extrap_obs
4) AUCinf_pred
5) AUCinf_D_pred
6) AUC_%Extrap_pred
I am little or not aware of many of them. I would be much grateful if
you kindly educate me what those parameters are and what are all the
significants of each parameters in calculating the extent of
bioavailability with respect to single and multiple doses.
Thanks & Regards,
Habeeb Ibrahim AR,
Exe.CRA,
Wellquest Clinical Research,
Nicholas Piramal India Ltd.,
4th Floor, Mirra Kamshetty Mall,
Ramanthapur,
Hyderabad - 50 00 13,
India
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The following message was posted to: PharmPK
Dear Habeeb,
The "obs" and "pred" endings refer to how the AUCs was extrapolated to
infinity. "obs" uses the observed Clast/LambdaZ where "pred" uses the
predicted value of Clast/LambdaZ. This prediction comes from the log-
linear
regression used to estimate LambdaZ. AUCall will be the same as AUClast
unless there are concentrations equal to zero at the end of the
curve. In
this case AUCall also contains the area (Tzero-Tlast)*Clast/2 where
Tlast is
the time of the last quantifiable concentration (Clast) and Tzero is the
time of the zero concentration AFTER Tlast. AUCinf_D_xxxx is simply the
AUCinf of interest (xxxx=obs or pred) divided by dose. As such it
happens to
be the inverse of CL (or CL/F for extravascular dosing). AUC_%
Extrap_xxx is
the percent of AUCinf that was extrapolated beyond Clast (i.e.
100*(AUCinf-AUClast)/AUCinf).
Bottom line...
Report AUClast, AUCinf, and AUC_%Extrap. The choice of "obs" or "pred"
versions is less critical, but should be consistent from study to
study when
submitting data to regulatory agencies. AUC_%Extrap should be small
(<10%).
Values above 25% indicate that you need to consider sampling for a
longer
period of time, improving the sensitivity of your assay, or both.
Cheers... Brian
Brian M. Sadler, PhD
Strategic PK Consulting, LLC
1209 Seabrook Avenue
Cary, NC 27511
USA
bsadler1.-at-.nc.rr.com
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Dear Habeeb,
It may be useful to you and others to download a list describing the
formulas or equations of some 75 PK parameters computed by our PK
Solutions Noncompartmental Pharmacokinetics Data Analysis software -
the easy way to do and understand pharmacokinetics analysis. The
various AUC calculations you mentioned are included in the list.
The PK equations can be viewed at www.SummitPK.com/equations/
equations.htm and downloaded as a pdf or interactive HTML file (go to
Download Page).
Hope this is helpful,
Regards,
David S. Farrier
/\ /\
SummitPK.com /\ / \ /\ / \
/ / / /\ / \
================================================
David S. Farrier, Ph.D. Phone: 970-249-1389
Summit Research Services Fax: 970-249-1360
68911 Open Field Dr. Email: DFarrier.at.SummitPK.com
Montrose, CO 81401 Web: http://www.SummitPK.com
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The PK equations can be viewed at:
www.SummitPK.com/equations/equations.htm
and downloaded as a pdf
or interactive HTML file (go to the Download Page).
[The link in the original message was wrapped around and difficult to
use - db]
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The following message was posted to: PharmPK
Hello Habib,
WinNonlin NCA parameter definitions, and their calculation formulas,
can be found under Help | Topics | NCA | Computational details for
WinNonlin's noncompartmental analysis engine. Additionally, the
program includes a set of example datasets and NCA models. We
recommend using the Examples Guide, which installs to the WinNonlin
\User Docs folder, to familiarize yourself with the software. If you
have any specific questions, please feel free to contact us via
support.-at-.pharsight.com.
Sincerely,
Christopher Mehl
Pharsight Software Support
Email: support.at.pharsight.com
Web: http://www.pharsight.com/support/support_sflogin.php
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