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Any suggestions on what would be the most appropriate equation to
estimate vancomycin concentration in the CSF following iv doses of
varying infusion times?
I would like to assume a two-compartment model for distribution and
elimination of vancomycin.
[You might start with
bottom of the page choose peripheral compartment and then finger print
method... ;-) or just use a program like boomer or WinNonlin to
estimate using numerical estimation. You have the parameter values...
[PS I've recently updated the online PharmPK archive and the Course on
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It sounds like you need to make a population model of
Vancomycin under those circumstances, based on serum data, probably 1
peripheral compartment to represent the rest of the nonserum part of
the body, as you suggest, and then another peripheral compartment to
represent the CSF. You will need to get rich data from the serum
levels, and as many CSF samples as you can from each patient.
One problem seems to be that of developing a reason for doing
the CSF samples. Clearly, at any time is it indicated to get CSF for
any other reason, you should get one for the vanco concentration. You
might also get a full appraisal of the CSF at each time, such as
sugar, albumin, cells, etc, for correlation with these important other
things, and probably a culture as well.
Is there any data already from the literature?
Having obtained your data, how do you propose to weight each
serum and CSF data point? Fisher information, not CV%, is by far the
best way to do this, as discussed profusely in PharmPK a couple of
months earlier. I am sorry that David felt he had to shut off that
discussion, as it was just getting good, with many interesting ideas
coming out from several people that really needed to be discussed. I
would invite anyone who is interested in the problem of correct
weighting of lab data to go to David's archives on this subject, read
them closely, and then to contribute their point of view here once
All the best for the New Year,
All the best,
Roger W. Jelliffe, M.D. Professor of Medicine,
Division of Geriatric Medicine,
Laboratory of Applied Pharmacokinetics,
USC Keck School of Medicine
2250 Alcazar St, Los Angeles CA 90033, USA
Phone (323)442-1300, fax (323)442-1302, email= jelliffe.-at-.usc.edu
Our web site= http://www.lapk.org
[This version of the archive index has the previous discussion at
I'm sorry if I cut this LLOQ discussion off too early but it seemed to
be going circles :-) - db]
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What is your basis for assuming a two compartment model? Do the plasma
profiles show a typical distribution phase followed by a long a
elimination phase? You might want to graphically analzye your data and
then come up with a model.
[Standing on shoulders? - db]
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