# PharmPK Discussion - AUC inf Vs Auc all

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• On 8 Nov 2005 at 20:57:22, "Chandra Mannem" (chandrasmannem.-at-.hotmail.com) sent the message

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Hi All,

I was calculating AUC all and AUC inf value but I am getting AUC inf
smaller than AUC all. Is this possible? If so can you please let me
know under what situations?

Can anybody let me know is there is any difference in AUC calculations
when considering single and multiple dose?

Thanks,
Chandra

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• On 9 Nov 2005 at 16:59:03, stefano.6.zamuner.at.gsk.com sent the message

Dear Chandra,
Yes, it is possible. Although unusual.

AUCall is calculated up to the last time point. In case of a BQL value
at the last measured timepoint (treated as zero conc.), AUC will be
extrapolated including the area under the curve between AUClast and the
last timepoint.
If this extrapolation is greater than the log-linear extrapolation done
for AUCinf, then AUCall>AUCinf

I would never report it, I would definitely recommend to use AUClast
(calculated up to the last quantifiable conc.)

Regards

Stefano

Stefano Zamuner, PhD
Clinical Pharmacokinetics/Modeling and Simulation
Psychiatry
Verona
Tel. +39-045-8219519
Fax +39-045-8218191

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• On 10 Nov 2005 at 11:15:34, Jagannath Kota (Jagannath.Kota.-at-.vcp.monash.edu.au) sent the message

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Dear Chandra,
I think the AUC inf should be at least a very small fraction greater
than the AUC 0-t. Logically AUC inf is AUC 0-t + (Clast/Kel), so you are
adding a fraction to the AUC 0-t.
Check if you have taken the negative value of the Kel, where you are
actually subtracting from AUC 0-t rather than adding the fraction. As
you calculated the Kel from the slope which is a negative value, there
are chances of accidentally taking a negative value for Kel. I am sure
you know this but in any case where we complete leave it to MS Excel!!
Hope this helps,
Jagannath
PhD Student
Victorian College of Pharmacy
Monash University
Parkville
VICTORIA 3052
AUSTRALIA
Work: +61 03 9903 9525

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• On 10 Nov 2005 at 11:43:27, Jagannath Kota (Jagannath.Kota.-at-.vcp.monash.edu.au) sent the message

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Dear Chandra,
I am sorry for my previous mail. I haven't realised until Stefano
pointed it out.
Jagannath

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• On 10 Nov 2005 at 09:33:22, "Porzio, Stefano" (Stefano.Porzio.-a-.ZambonGroup.com) sent the message

The following message was posted to: PharmPK

Dear Stefano,
I apologize, however I suspect I have not really understood: you say
that

<< AUCall is calculated up to the last time point. In case of a BQL
value
at the last measured timepoint (treated as zero conc.), AUC will be
extrapolated including the area under the curve between AUClast and the
last timepoint.
If this extrapolation is greater than the log-linear extrapolation done
for AUCinf, then AUCall>AUCinf>>

Can you provide us a numerical example?
I believe that by numerical exemplification I can easily understand...
I apologize again, thank you very much in advance

Best regards

Stefano Porzio
Inpharzam Ricerche SA
Zambongroup
Taverne
Switzerland

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• On 10 Nov 2005 at 16:08:50, helmut.schuetz.at.bebac.at sent the message

The following message was posted to: PharmPK

Hi Chandra!

I think that 'AUCall' is Pharsight's 'invention' ;-)

Suggestion: never use it; if your software calculates it, simply ignore
it...

have a look at: http://www.boomer.org/pkin/pk/AUCinf.jpg

Best regards,
Helmut

--
Helmut Sch=FCtz
BEBAC
Consultancy Services for Bioequivalence and Bioavailability Studies
Neubaugasse 36/11
1070 Vienna/Austria
tel/fax +43 1 2311746
http://BEBAC.at
Bioequivalence/Bioavailability Forum at http://forum.bebac.at
http://www.goldmark.org/netrants/no-word/attach.html

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• On 10 Nov 2005 at 16:43:48, stefano.6.zamuner.aaa.gsk.com sent the message

AUCall is AUClast plus the area of the triangle assuming that the next
time point after Clast is zero

Try this.

0.25 228.7
0.5 262.8
1 314.3
2 309.2
4 215.3
6 160.5
8 118.8
12 5.4
24 0

Stefano

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