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AUCtau vs partial AUC

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#1 mhvo2001@gmail.com

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Posted 10 October 2016 - 07:25 PM

I have a fixed dose combination drug given every 12 hours (tau = 12). One of the component of the FDC has very long half-life. The t1/2 values are 21 hrs for parent compound and the 3 active metabolites are 26 hrs for metabolite A, 31 hrs for metabolite B, and 50 hrs for metabolite C. 

 

Blood sampling was collected for 12 hrs (a dosing interval). Because of the long t1/2 of the metabolites, I was not able to estimate lamda-z to estimate AUCtau for the metabolites. However, WNL was able to calculate AUC(0-12) for them since most subjects have samples collected at 12:10 hrs (a little longer than the end time of AUC(0-12).

 

Can I used AUC(0-12) to report as AUCtau since AUC(0-12) and AUCtau are the same in this case.

 

Thanks very much for your advice!



#2 Simon Davis

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Posted 11 October 2016 - 05:13 AM

MHVO, in principle that sounds fine to me.  I'd be interested to check an example of your data because if AUC0_12 is generated I would also expect AUCtau to be generated (and be identical to 0-12) even without a Lamda_z

 

  Simon.



#3 mhvo2001@gmail.com

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Posted 11 October 2016 - 02:45 PM

Thanks Simon!  

 

AUCtau needs to have a dose to be calculated while AUC12 does not. We left the dose for metabolites blank, which caused AUCtau not calculated. Adding the parent dose for metabolites (or any number for dose) fixed the issue and AUCtau and AUC12 came out the same.  Interesting of how the requirements for WNL to calculate AUCtau and AUC12 are different but giving the same values. 

 

I am also testing out another case with Tlast < 12, this case both AUCtau and AUC12 need to have lamda-z to be calculated, which made sense.  



#4 mittyright

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Posted 11 October 2016 - 10:23 PM

Dear MHVO,

 

Thanks Simon!  

 

AUCtau needs to have a dose to be calculated while AUC12 does not. We left the dose for metabolites blank, which caused AUCtau not calculated. Adding the parent dose for metabolites (or any number for dose) fixed the issue and AUCtau and AUC12 came out the same.  Interesting of how the requirements for WNL to calculate AUCtau and AUC12 are different but giving the same values. 

 

I am also testing out another case with Tlast < 12, this case both AUCtau and AUC12 need to have lamda-z to be calculated, which made sense.  

 

WNL does not check Tau column when Dose is empty, resetting Dose and Time to 0. That's why you do not see AUCtau. Please check Warnings/Errors output sheet.







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