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Dear all,
I would like to know your opinions regarding Cmin,ss. Assuming that
concentration data from a complete period of T hours are available for
each subject, so that one minimum of conc. is observed at the beginning
(t = nT) and the other at the end (t = nT + T), should I choose the
value at the time nT, at the time nT+T or Cmin,ss = min [C(nT) ,
C(nT+T)], which is the value usually calculated by our software
(WinNonlin)?
I think this last option would introduce an additional source of
variation due to different sampling times, that is, for some subjects
Cmin could be taken at t = nT and for the rest at t = nT+T. Do you know
about any regulation regarding this topic?
I'd really appreciate your help. Thanks in advance
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The following message was posted to: PharmPK
WinNonlin does not use Cmin,ss = min [C(nT) , C(nT+T)]
It uses min [for all concentrations obtained from nT to nT+T].
For drugs with delayed gastric emptying, the concentration taken after
nT can be the Cmin.
Susan
Susan E. Shoaf, Ph.D.
Sr. Clinical Pharmacokineticist
Otsuka Maryland Research Institute
Rockville, MD
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Dear Susan, your right, WinNonlin uses the minimum conc. whitin the
period, maybe I was not clear enough (and I'm sorry my English!!). I was
referring to a case (in theory) in steady state with a single
fluctuation where you can see 2 minimum values, although they could not
be observed at exactly nT or (n+1)T (i.e. an oral once-a-day CR
formulation). I was wondering if I should fix the minimum of such
fluctuation, for instance the first minimum, or let the software decide
(taking the first Cmin for some subjects and the second for the rest)?
Thanks again.
Marcelo
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