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Will this design have an effect on any of the PK parameters like Cmax,
or AUC? YES.
typically take less than 20% of total blood volume during the course of
serial bleeds. total blood volume is usually 5-7% of the rats body
weight.
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Dear All,
Thanks for suggestions on rat blood sampling. But even after taking
about 5.5 - 6 ml of the blood from a rat (140 - 160g) I have noticed
the animals are quite healthy. My major concern is how would that
much volume affect the PK parameters i.e in which way Cmax or AUC be
affected.
Secondly I have tried another design of sampling, i.e I take 5 rats
at each time point i.e 5 rats at 5 min, 5 at 15 min and so on. I kill
5 rats at each time and pool the serum sample. Is this design OK in
Preclinical PK studies.Please suggest.
Thirdly one of my colleague in Toxicology Lab is doing 28 day tox.
study for one of our compounds in rats. He has observed that after 7
days there is lot of phlebitis in the tail vein and he is not able to
inject any more. Can anyone suggest some ways to decrease this
phlebitis.
Suggestions would be of great help.
"WISHING YOU ALL A VERY WONDERFUL MILLENIUM"
M.Khan
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Dear Mubeen,
we are using rats with body weights of about 250 g for our PK-studies. We
never take more than 2.5 ml of blood! If you take more blood the sampling
will significantly contribute to the elimination of a compound with a small
volume of distribution. The strongly reduced cell content of the blood would
effect the PK of compounds which were strongly distributed into blood cells.
Your second approach will work in principle with iv administrations. To our
experience, the interindividual variability of the bioavailability of the
test compound are often so large, that you cannot calculate PK-parameters
from concentrations which were taken from different animals after oral
administration. In this case it might be useful to use NONMEM for the
calculation of PK-parameters. Why do you need so much blood? You should
consider more sensitive analysis.
Good luck and best wishes for the new year
H.Beier
-------
Dr. Horst Beier Tel.: +49-(0)241-569-2419
Gr=FCnenthal GmbH Fax.: +49-(0)241-569-2430
Dept. of Pharmacokinetics (FE-PK)
Zieglerstr. 6 Mailto: Horst.Beier.aaa.grunenthal.com
D-52078 Aachen, Germany
-------
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Hi,
Couple of months back there had been a discussion on the rat blood
volume.
We are doing PK screening of some NCE's in rats. Our protocol involves
serial sampling from rats. We use rats in the range of 220 - 275g and
we take about 7 - 8 samples from 0 to 4 hrs.
Each blood sample volume is approx. 300 - 400=B5l which means about 3 -
3.5ml total blood and we get pretty consistant results.
Is that fine. If not I would be specifically interested to know how
would this effect the PK behavior of our compounds in terms of various
PK parameters.
Thanks : M.Khan
[The earlier discussion is indexed on=20
http://www.boomer.org/pkin/PK_2000.html - db]
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[Two more replies - db]
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Date: Mon, 03 Apr 2000 08:48:41 -0500 (EST)
From: "Alfredo Sancho 301-827-7310 FAX t-"
Subject: Re: PharmPK Blood volume from rat
To: "postmaster"
MIME-Version: 1.0
Posting-date: Mon, 03 Apr 2000 08:48:42 -0500 (EST)
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M.Khan:
Briefly there are at least two different issues that come to my mind...
1- Total rat blood volume. That is, any change in the total blood volume
may affect not only the "normal" behaviour and metabolism of the animal,
but also the kinetics of the drug you may be studying.
2- Protein binding fraction. If your drug has a protein binding fraction,
how can you account for the effects of the blood you withdraw.
The most common way to address these issues is by injecting an equal amount
of normal "rat" saline as to that of withdrawn blood, after each sampling
time. This will maintain the blood volume close to the original, but the
protein binding and other metabolic related issues may still exist. Also
keep in mind that the hemodynamics of normal blood may be different than
blood and saline; therefore, it may affect the distribution and movement of
your drug in and out of the target tissue and others.
There is no simple nor easy answer. That is why it is so important to
document the total volume of withdrawn blood, the time over which the blood
sampling was performed, the condition of the animals, and to understand the
behaviour of your drug as affected by the above mentioned issues.
Regards,
Alfredo R. Sancho, Ph.D.
Clinical Pharmacologist
---
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Date: Mon, 03 Apr 2000 09:45:40 -0500 (EST)
From: "Ronald Kavanagh 301-827-4254 FAX 301-827-4264"
Subject: Re: PharmPK Question regarding glomerular filtration process
To: "postmaster",
"Multiple recipients of PharmPK - Se"
MIME-Version: 1.0
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I suggest that you also consider if you have a valid test question and
whether it should be thrown out.
On one hand you can interpret the question slightly differently if you
change the wording to glomerular filtration rate (which is what I think
you may have intended originally).
Second, since you have an issue, this suggests a problem with the
question itself, or with the teaching of the material.
The American Association of Colleges of Pharmacy. Published a Handbook
on the design of instruction in pharmaceutical education many years ago
that discusses test question validation and how to determine if a
question should be thrown out. Alternatively, texts on education may be
helpful to you.
Ron Kavanagh
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[Three replies - db]
Date: Mon, 03 Apr 2000 08:02:17 -0400
From: "Cotler, Stanley {NCDS~Nutley}"
Subject: RE: PharmPK Blood volume from rat
To: "'PharmPK.-a-.boomer.org'"
The total vol is equal to approximately 6.0% of a rat's body weight.
I would not take any more than 10% of total volume over the course of
a day and would give back donor blood to reduce stress of blood
depletion. This will reduce hypovolemia and effects on the
parameters measured.
Stanley C
Stanley Cotler
Department of Non-Clinical Drug Safety
Phone (973) 235-2857 Fax (973) 235-7010
E-Mail Stanley.Cotler .at.Roche.com
Nutley
---
Date: Mon, 03 Apr 2000 15:10:54 +0200
From: Margareta Hammarlund-Udenaes
Reply-To: margareta.hammarlund-udenaes.at.biof.uu.se
Organization: Uppsala Universitet
X-Accept-Language: en,sv
To: PharmPK.aaa.boomer.org
Subject: Re: PharmPK Blood volume from rat
We normally limit our sampling to 10 % of blood volume, i.e. about 2 ml
to be on the safe side. You would need to do a comparative study with
late-time concentrations with and without the extensive sampling
procedure to be able to know if the sampling influence your results.
Margareta Hammarlund-Udenaes
---
Date: Mon, 03 Apr 2000 15:07:20 -0400
From: "Nabil B. Darwazeh"
To: PharmPK.-a-.boomer.org
Subject: PharmPK Re: Blood volume from rat
If your concern is that the removed blood will affect the PK of the
drug, you may want to replace the removed blood with fresh from a
donor.
Regards
Nabil
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[Two replies - db]
=46rom: horst.beier.aaa.grunenthal.com
To: PharmPK.-at-.boomer.org
Subject: AW: PharmPK Blood volume from rat
Date: Tue, 4 Apr 2000 08:36:42 +0200
Your design is ok as far as I can see. In principle we take the same volume
of blood with a comparable number of samples. For pilot studies this is
acceptable. For full preclinical investigations you should think about
distributing the samplings over several rats. Evaluation of the
pk-parameters could be done with NonMem. In this case you need 3 to 5 time
more animals depending on the number of samples.
Have a nice day
Horst
---
Date: Tue, 4 Apr 2000 10:31:55 +0100
=46rom: Eric.Magnan.aaa.beaufour-ipsen.com
Subject: R=E9f:PharmPK Re: Blood volume from rat
To: PharmPK.-a-.boomer.org
Regarding to GLP:or international guidelines
Circulating blood volume removed in 24H 7.5% recovery period 1 week
=20 10% 2 weeks
=20 15% 4 weeks
=46or this kind of sampling above no stress is related.
The higher volume (20%) is intended to facilitate serial blood sampling for
toxico or PK purpose where multiple, small samples are usually=20
required. However
you should be remembered that the consequential haemodynamic effect of taki=
ng
such large vol. may affect the calculated half life.
Magnan E
Laboratoires PharmaBiotech- PK unit.
83330 FRANCE
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From the table of Administration volumes considered good practice (possible
maximal dose volumes)
In Rat you can inject IV bolus : 5ml/kg/site
or 20ml/kg/site with slow injection.
If you try too large volume 1st:ill be a stress for the animal and you will
modify the homeostasis
2nd: you'll modify the kinetics parameter of the drug.
best regards
E Magnan
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Dear Mubeen Khan
This is a useful way to assess the influence of sample volume from
rats on the pk. you can just draw blood at the last time point in a
control group,and compare the concentration with the last point
concentration of serial samples to see if any influence of sample
volume or time points on the pk.
John Chan Ph.D
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)