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The following message was posted to: PharmPK
Dear PKusers,
I want specify better my doubt.
The objective of my study is to investigate the toxicity/
toxicokinetic of a test item in dogs after daily intravenous infusion
for 24 hours for a 4 week treatment period.
Blood will be sampled after the first 24 hrs of infusion (on the
morning of day 2) and then after 14 days of infusion (on the morning
of day 15) and then on day 29. No sampling will be perfomed after the
end of infusion.
My question is if it is possible to calculate the STD parameters in
this type of administration? Is it correct to determinate the t 1/2
of a drug if given by continous infusion?
So the following definitions for the PK parameters could be write in
the study protocol?
The toxicokinetic analysis will be conducted according to a standard
non-compartmental analysis.
The following parameters will be calculated:
Cmax : maximum observed plasma concentration
tmax : time to Cmax
Clast : The concentration value obtained at sampling time Tlast.
Tlast : The last sampling time at which a quantifiable
concentration is found.
AUClast : The area under the plasma concentration versus time curve
up to sampling timeTlast, calculated by linear trapezoidal rule.
t 1/2 : elimination half-life
thank you very much.
please help me its urgent.
Dario Salerno, Chem.Pharm.D.
Study Director
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The following message was posted to: PharmPK
Dear Dario,
If I understand you correctly, you will infuse the drug over 28 days,
and
take samples after 1 day, 14 days and 28 days. This will not allow
you to
calculate any of the PK parameters you listed. If the half-life is
less than
about 6 hours, the expected concentration at all time points is the
same,
and clearance can be calculated, but none of the other PK parameters.
If the half-life is longer, you might get a crude estimate of half-
life from
the increase of the concentration, but this is not the preferred
method to
estimate half-life.
Best regards,
Hans Proost
Johannes H. Proost
Dept. of Pharmacokinetics and Drug Delivery
University Centre for Pharmacy
Antonius Deusinglaan 1
9713 AV Groningen, The Netherlands
tel. 31-50 363 3292
fax 31-50 363 3247
Email: j.h.proost.at.rug.nl
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The following message was posted to: PharmPK
Colleagues:
May I ask Dario Salerno for the justification of a study that
delivers an
infusion 24 hours a day for 28 days to a dog? Apart from questions
relating to animal welfare I am surprised that there is a real
possibility
of altered kinetics after such a long period if Pk is the aim of the
study
(and not toxicology).
Thanks
Andrew Sutton
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)