# PharmPK Discussion - Renal clearance from pooled urine

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• On 3 Jun 2008 at 08:41:23, renu singh (singrenu.-a-.yahoo.com) sent the message

Hi,

I would be thankful if any one can provide me insight into calculating
renal clearance, when you have pooled urine but plasma samples are
timed.
I have seen some references where average plasma concentrations or mid
point plasma concentration is used. I am not able to understand the
justification of using either of these.

Thanks,
Renu

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• On 4 Jun 2008 at 09:42:24, "jayasagar.g" (jayasagar.g.at.advinus.com) sent the message

The following message was posted to: PharmPK

For calculating renal clearance you need
1) Amount recovered in urine for the duration (urine conc X volume of
urine)
2) AUC of plasma concentration time profile for that duration.
I understand you have both of these values then the CLrenal AUCplasma/Ae
Where 'Ae' is the amount recovered in urine.

Regards,
Jayasagar Gundu

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• On 4 Jun 2008 at 11:16:42, "jayasagar.g" (jayasagar.g.aaa.advinus.com) sent the message

The following message was posted to: PharmPK

Regards,
Jayasagar Gundu

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• On 4 Jun 2008 at 23:02:21, "Vinu Menon" (vinucops.at.gmail.com) sent the message

Dear jayasagar

There is a problem for the renal clearance formula. You have written
it as AUC/Ae. If it is so the unit will become h/mL, which is not
correct for the clearance it should be mL/h.

I think the formula should be Ae/AUC plasma.

I would also add a point that the time duration for urine collection
should be atleast equal to 5 halflives

regards

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• On 5 Jun 2008 at 11:36:00, ebes.frieda.-a-.kendle.com sent the message

Hi,

Indeed the way of calculation is Ae/AUC and make sure to correct for
your units (h to min as needed, the units for weight and volume). To
do it correctly, the time interval for calculating AUC should be the
same as the time interval of the urine collections and not necessarily
cover 5 half-lives.
You need to collect urine for five half-lives if you want to know
which fraction of the dose is excreted in the urine.

Frieda

Kendle
the Netherlands

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• On 5 Jun 2008 at 15:34:28, "J.H.Proost" (J.H.Proost.at.rug.nl) sent the message

The following message was posted to: PharmPK

Dear Vinu,

You wrote:

> I would also add a point that the time duration for urine collection
> should be atleast equal to 5 halflives

This is not necessary. Please note that Jayasagar correctly wrote that
AUC and Ae should refer to the same time interval. This interval may
be from zero to infinity (i.e. in practice to at least equal to 5
halflives). However, any interval can be used. In such cases AUC does
not reflect total AUC (so, total clearance cannot be calculated), and
Ae does not reflect Ae at infinity (so, fraction excreted in urine
cannot be calculated). But renal clearance can be calculated reliably
from Ae/AUC provided that AUC and Ae are determined over the same time
interval.

best regards,

Hans Proost

Johannes H. Proost
Dept. of Pharmacokinetics and Drug Delivery
University Centre for Pharmacy
Antonius Deusinglaan 1
9713 AV Groningen, The Netherlands

Email: j.h.proost.-at-.rug.nl

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• On 5 Jun 2008 at 15:34:28, "J.H.Proost" (J.H.Proost.-a-.rug.nl) sent the message

The following message was posted to: PharmPK

Dear Vinu,

You wrote:

> I would also add a point that the time duration for urine collection
> should be atleast equal to 5 halflives

This is not necessary. Please note that Jayasagar correctly wrote that
AUC and Ae should refer to the same time interval. This interval may
be from zero to infinity (i.e. in practice to at least equal to 5
halflives). However, any interval can be used. In such cases AUC does
not reflect total AUC (so, total clearance cannot be calculated), and
Ae does not reflect Ae at infinity (so, fraction excreted in urine
cannot be calculated). But renal clearance can be calculated reliably
from Ae/AUC provided that AUC and Ae are determined over the same time
interval.

best regards,

Hans Proost

Johannes H. Proost
Dept. of Pharmacokinetics and Drug Delivery
University Centre for Pharmacy
Antonius Deusinglaan 1
9713 AV Groningen, The Netherlands

Email: j.h.proost.at.rug.nl

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