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The following message was posted to: PharmPK
Hello,
I found the message attached below on an old PharmPK Discussion page
(Sept,
2000) and I am interested in finding the literature source for the rat
Percent Body Weight Factors listed. If you can, I would appreciate
it very
much if you would send me the appropriate citation from the published
literature.
Thanks very much,
Don Slaughter, WP75-100
Don Slaughter
Department of Drug Metabolism
Merck & Co., Inc.
Sumneytown Pike
West Point, PA 19486
Phone: (215) 652-5095
FAX: (215) 993-3533
e-mail: donald_slaughter.-a-.merck.com
--
Sender: PharmPK.at.boomer.org
Reply-To: "David S. Farrier"
Mime-Version: 1.0
From: "David S. Farrier"
Date: Thu, 21 Sep 2000 00:03:00 -0400
To: david.at.boomer.org
Subject: PharmPK DPM to concentration
Dear Qing,
Here are some useful equations:
The key to your question involves knowing how to use the specific
activity
of a dose form to convert radioactivity to equivalent weights. Assume
that
you measured the specific activity of your dose form in units of dpm/ug.
Further assume that you measured your plasma or other tissue samples in
replicate and computed an average activity concentration in DPM/g
Then,
(CASE 1) for contiguous tissues (those which can be excised in whole
like
liver, brain, kidney, etc).:
Average Total Activity (DPM) Average Activity Concentration (DPM/g) x
Total Sample (g)
(CASE 2) however, for non-contiguous samples (those which usually can
only
be sampled in part, such as blood, body fat, skin, etc.):
Average Total Activity (DPM) Ave. Activity Conc. (DPM/g) x ( %BW
Factor/100) x Terminal BW (g)
Where Terminal BW = Body Weight of the carcass at termination.
Some values often quoted for the Percent Body Weight Factor (%BW Factor)
for the rat are:
Blood 4.04
Plasma 2.35
Fat 10.60
Muscle 45.40
Plasma 2.35
You can then proceed to calculate the average amount of dose form in the
total sample as follows:
Average Total Amount (ug) Average Total Activity (DPM) / Specific
Activity (ug)
Alternately, you can calculate the concentration of dose form in the
sample
as follows:
Average Amount Concentration (ug/g) Average Activity Conc. (DPM/g) /
Specific Activity (DPM/ug)
Finally, you can calculate the percent of dose in the sample as follows:
Percent of Dose 100 x Average Total Activity (DPM) / Total Dose
Applied (DPM)
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The following message was posted to: PharmPK
Don,
There is no really complete reference in the literature.
The best is:
Caster et al. Proc. Soc. Exp. Biol. Med. 91:122-126 (1956)
Dale
PharmPK Discussion List Archive Index page
Copyright 1995-2010 David W. A. Bourne (david@boomer.org)