Back to the Top
The following message was posted to: PharmPK
Dear All,
I am wondering whether to use AUC o-t or AUC o-inf
to calculate absolute BA.
Thanks in advance.
CALI
Back to the Top
The following message was posted to: PharmPK
CALI,
You have to use AUCo-->oo if the bioassay method is
sufficiently sensitive and the drug's terminal
half-life is reasonably long. Otherwise, you should
use AUCo-->tlast as a surrogate of AUCinf provided
that the ratio AUCtlast/AUCinf > 0.8.
Regards,
D. Terziivanov
Back to the Top
We use AUC o-inf to calculate absolute BA.
Prof N Bahi
Back to the Top
The following message was posted to: PharmPK
I assume that you are talking about IV data, as to my knowledge absolute
bioavailability is the terminology for IV data. In that case AUCo-inf
should
be considered for calculating absolute bioavailability.
For calculating extravascular bioavailability too, it is advisable to
use
AUCo-inf to the extent possible.
Hope this helps,
Jagannath
PhD Student
Victorian College of Pharmacy
Monash University
Parkville
381 Royal Parade
VICTORIA 3052
AUSTRALIA
Work: +61 03 9903 9525
Back to the Top
The following message was posted to: PharmPK
Dear All
We have conducted an absolute bioavailability (F) study (iv Vs. oral)
in dogs (n=3). The observed mean value is 130% (individual values
were also > 100%). I am wondering how this is possible. I have two
questions:
1. What are the reasons for observing F - >100% ?
2. What is the contribution of enterohepatic recycling on AUC upon
oral and iv administration ?
Thanking you in advance.
Vinay
Back to the Top
The following message was posted to: PharmPK
Short of knowing the specifics of your compound or study design but
assuming no experimental error, we can speculate on a few possible
areas where we can start looking for an explanation.
Do you have nonlinear kinetics? Are the AUC values comparable between
the IV and PO dose?
Was the IV dose given in bolus? Could part of the IV dose have
precipitated out upon injection?
Did your sampling scheme allow you to adequately capture the AUC
measurement, especially for the earliest time points after the IV
dosing where there may be a rapid distribution phase?
Regards,
Back to the Top
The following message was posted to: PharmPK
Dear Vinay,
The following point maybe of help:
If there is a higher oral dose than IV dose , there
is possibility that saturation mechanism could happen
which could lead to non linear disposition of drug and
bioavailability (F) could be exagerated.In that
case you may evaluate a similar oral IV dosing to
rule this out.
thanks
Back to the Top
The following message was posted to: PharmPK
In addition to Yongqing's comments, are your calculations based on
AUC_inf or AUC-last and what is/was the ratio between these two values
for iv and po?
Kind regards,
Frederik Pruijn
Frederik B. Pruijn PhD MSc (Senior Research Fellow)
Experimental Oncology Group
Auckland Cancer Society Research Centre
Faculty of Medical and Health Sciences
The University of Auckland
Private Bag 92019
Auckland
New Zealand
Phone: +64-9-3737 599 x86939 or x86090
Fax: +64-9-3737 571
E-mail: f.pruijn.-at-.auckland.ac.nz
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)