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Due to carboplatin's nonlinear PK, one tries to sample patients at times
which wind up being in the middle of the night. In a teaching hospital it
would not be a big deal to have samples processed (plasma separated) in the
middle of the night but elsewhere it can be a real problem.
My question then is, what does one risk by spinning a sample in an
unrefrigerated centrifuge, then storing the plasma refrigerated over, say 8
h, then continuing by preparing ultrafiltrate in which to analyze free
carboplatin?
Any experience out there?
Thanks,
Bill O'Neil
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Hi Bill
> Due to carboplatin's nonlinear PK
Are you sure? I have not come across non-linearities in the PK of
carboplatin before. 75% of carboplatin is renally cleared by
filtration - therefore that cannot be capacity limited. Much of the
remainder is eliminated by non-reversible binding to proteins - which
also does not seem to be non-linear. None of the popPK analyses to
date have shown signs of non-linearities (at least that I am aware
of).
> My question then is, what does one risk by spinning a sample in an
> unrefrigerated centrifuge, then storing the plasma
> refrigerated over, say 8
> h, then continuing by preparing ultrafiltrate in which to analyze free
> carboplatin?
If you are trying to measure carboplatin then I suspect that this
would not be appropriate. Carboplatin seems to degrade rather
rapidly in plasma and serum. If you are trying to measure platinum
itself then I doubt it would matter.
If you can freeze the ultrafiltrate - preferably -80oC - then
stability will be fine.
However, I think the more important question is why you want to take
a sample in the middle of the night?
Regards
Steve
Stephen Duffull
School of Pharmacy
University of Queensland
Brisbane 4072
Australia
http://www.uq.edu.au/pharmacy/duffull.htm
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Passed on to me from Kendra Tutsch:
See
Erkman, Egorin et al, "Effect of storage on the binding of
carboplatin to plasma proteins", Cancer Chemother Pharmacol 35,
254-256 (1995)". The results were, store at -70 is OK, at -20 is not
suitable. So either UF right away or store at -70. I am finding some
studies where they are now just storing PK samples for carbo at -70,
without real time UF.
Paul Hutson, Pharm.D.
Associate Professor (CHS)
UW School of Pharmacy
777 Highland Avenue
Madison, WI 53705-2222
Pager: (608) 265-7000, #7856
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