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Dear all,
Can any one explain about the purpose of calculating ratio of AUCt to
AUCinf during PK Analysis
Thanks in advance
Regards
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The following message was posted to: PharmPK Hi,
IMHO, it represents the fraction of extrapolated AUC
relative to AUCinf, on the other hand. Ideally, we want that
extrapolated AUC as small as possible. After all, it's extrapolated,
not what we actually observe. So if the ratio of AUCt to AUCinf
is large enough (e.g.. > 90% or more), it means the extrapolated
AUC is less than 10% which is quite acceptable in perspective of
regulatory basis in some countries, especially in a bioequiva-
lence study. Usually the ratio of (1-AUCt/AUCinf) should be
less than 15% or 20%
Regards,
Yung-jin
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The following message was posted to: PharmPK
Dear sujatha,
AUCt to AUCinf ratio is calculated to see how much you are extrapolating
the data from the actually obtained one. As per guidance, only 20%
extrapolation (imaginary) is allowed. That means 80% of the result
should be from your data up to last measurable point. If you are not
getting 80%, we can conclude that there are problems with your sampling
time points.
Regards,
Muhiyideen
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Dear Sujatha,
The ratio is calculated to determine the fraction of the extrapolated
AUC (AUCinf) with respect to AUCt. If the extrapolated AUC is
considerably high (where the ratio is less than 0.8), the data may
have to be interpreted with due consideration to the likelihood of
associated error. This infact means that the sampling points were not
extended to the desired length of time and as a result the
extrapolated AUC is considerably greater than the AUCt calculated from
the experimental data, hope this helps, wish someone would educate me
further, regards, Jagannath
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Dear Sujatha,
When I first saw your question I wasn't sure if you meant AUCt
to be AUC(0 to tlast) or AUC(0-tau), where tau is the dosing interval.
If you meant the latter this ratio can be used to calculate a Predicated
Accumulation ratio which is then compared to an actual accumulation
ration in a multiple dose study.
On Day 1, after the first, (single) dose;
AUC(0-inf) Day 1/AUC(0-tau) Day 1
(gives a Predicated Accumulation ratio, where tau is the dosing
interval.)
On your steady state day;
AUCtau(steadystate)/AUCtau(single dose)
(gives an actual Accumulation ratio)
Comparing the two can help you in your assessment of Dose Linearity etc.
Best regards,
Simon.
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Dear Sujatha
AUC o-inf is calculated by summation of AUC o-t.
and ratio of (last measurable conc to Elimination phase contant)
During PK analysis if time point selected by you could be considered
well enough if you are getting higher ratio (>88%) of AUCt to AUCinf.
It shows time point selected by your is covering whole profile of drug
retention in body.
--
Regards,
Gaurav Shah
SPARC,Baroda
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Hi,
AUCt to AUCinf ratio is meaningless. The reason for this is that time
"t" is selected by a pharmacokinetician, consequently AUCt to AUCinf
depends on the pharmacokinetician choice.
With best regards,
Maria Durisova DSc (Math/Phys)
www.uef.sav.sk/durisova.htm
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Dear All,
I need some understanding on the ratio of AUCt to AUCinf. Generally we
read in literature that AUC%extrap should not be more than 20% for
reliable estimation of t1/2. Where do we get this figure and what is
the significance.
Regards
Dr. Tausif Ahmed
Metabolism and Pharmacokinetics
Ranbaxy Research Laboratories
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Dear Tausif Ahmed,
The reason for this is one single concentration [C(last)] in the
terminal phase has a high influence on the AUC(inf) values since
AUC(inf) = AUC(last) +[C(last)/Kel]. Where Kel is 0.693/t1/2. If the
analytical assay is not sensitive enough, the ratio of AUC (last) to
AUC( inf ) will be less than 80%. It is better to determine AUC (last)
with the most sensitive assay and taking blood samples for a time
period exceeding four T1/2. AUC(inf) is appropriate for drugs with
long T1/2 (>48 hours) provided that the ratio of [AUC(last)/
AUC(inf) ]exceeds 0.80.
Please also refer http://www.boomer.org/pkin/pk/AUCinf.jpg
Regards
Venkatesh
University of Groningen,The Netherlands.
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