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The following message was posted to: PharmPK
Dear Everyone,
I want to figure out the time of peak tissue concentration of
antibiotics based on the distribution half life and rate of an infusion.
Can anyone guide me as to the formula or available literature.
Thank you very much!
Alla Paskovaty, Pharm.D.
Clinical Coordinator, Antibiotic Management
Memorial Sloan-Kettering Cancer Center
NY, NY 10021
paskovaa.-at-.mskcc.org
[The larger of 3-5 distribution half-lives(?) and the infusion duration
- db]
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The following message was posted to: PharmPK
"Paskovaty, Alla/Pharmacy" wrote:
>
> I want to figure out the time of peak tissue concentration of
> antibiotics based on the distribution half life and rate of an
> infusion.
> Can anyone guide me as to the formula or available literature.
>
You will need to know at least 4 parameters -- not just one -- in order
to predict the peripheral compartment time course. The simplest model
is a two compartment model. It's parameters can be expressed in a
variety of ways but you ALWAYS need to know four of them to define the
model e.g.
A, B, alpha, beta (this parameterization also requires the input
process to be defined)
or
clearance, central compartment volume, distribution half-life,
elimination half-life
or
clearance, inter-compartmental clearance, central volume, peripheral
volume.
Once you have the parameters then I can suggest how to predict the time
of peak conc in the peripheral compartment.
--
Nick Holford, Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New
Zealand
email:n.holford.aaa.auckland.ac.nz tel:+64(9)373-7599x86730 fax:373-7556
http://www.health.auckland.ac.nz/pharmacology/staff/nholford/
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The following message was posted to: PharmPK
Dear Alla,
Kinetics in tissues can not definitely be determined on basis of blood
or plasma
data solely. Depending on the properties of the substance, data like
time to
peak and elimination half time may vary significantly between different
organs
depending on blood flow rates and permeabilities. This can not be
determined
from the plasma curve with descriptive PK-models (one, two, three...
compartments). A good estimation is only possible with physiology based
PK-models, which describe each organ as a single compartment and regard
the
specific physiological parameters as blood flow rates and substance
specific
properties as permeabilities explicitely.
For more information see: www.pk-sim.com
Regards
Walter Schmitt
Bayer Technology Services GmbH
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