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Dear members,
I am facing one situation where I gave the drug dose (10mg/kg) to the
rats and blood collection (0.5 ml) was taken at 0, 1, 4 and 6 hours
later. After one week of washout period, the same dose was given and
blood collection performed at 45 min, 2, 3 and 5 hours after drug
administration. This approach was used by recomendation of IACUC due
the limitation in collecting all time points in one day. Since the
rats gained weight during this one week period the total dose given
for each animal was not the same. Does anyone have any suggestion how
can I link the dose (mg/kg) to the weight of the animal using
WinNonlin?
Thanks all,
Whocely Victor de Castro
Graduate Student
University of Florida
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Dear Whocely Victor de Castro,
In the dosage regimen area of WinNonlin, when you set the units,
select the normalize for body weight (kg) option. The one of the
things to think about is yes, the animals body weight changed, but as
in veterinary medicine, the dose did not (10 mg/kg), just the total
amount of drug given. I would be concerned if the animals had major
changes in body composition?
Hope this helps.
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The following message was posted to: PharmPK
Hi
> In the dosage regimen area of WinNonlin, when you set the
> units, select the normalize for body weight (kg) option. The
> one of the things to think about is yes, the animals body
> weight changed, but as in veterinary medicine, the dose did
> not (10 mg/kg), just the total amount of drug given. I would
> be concerned if the animals had major changes in body composition?
I was recently involved in a study in rats in which the rats doubled
their
size during the course of the study (not due to obesity). The CL and Vd
also changed during the study in relation to the weight of the rat. We
modelled this data in NONMEM and weight turned out to be an important
predictor of within rat variability in the values of the parameters. In
this case heterogeneity between rats was less important than systematic
changes within a rat.
Steve
--
Professor Stephen Duffull
Chair of Clinical Pharmacy
School of Pharmacy
University of Otago
PO Box 913 Dunedin
New Zealand
E: stephen.duffull.-a-.otago.ac.nz
P: +64 3 479 5044
F: +64 3 479 7034
Design software: www.winpopt.com
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The following message was posted to: PharmPK
Hello
I am sure you will find the linking solution for dose and weight.
Objectives of your experiment are not available, but still I can
suggest following. You will probably need to know quantum of effect
of weight gain on PK to take further decision. This can be done by
giving same total dose to additional two groups using same protocol.
If necessary use multiple dose levels. Of course this is an
additional experiment.(Obviously you need to conduct both the
experiments simultaneously). Then compare difference (or change) and
absolute PK parameters in these two experiments.
WBR
Dr.Prashant
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