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The following message was posted to: PharmPK
Dear Group,
I am working on a compound that is administered as a 3 hr constant IV
infusion. The plasma concentration data from a number of patients
showed an
unusual behavior, specifically the Cmax was observed about 0.5~1 hr
after
the start of infusion followed by a decline in the drug
concentration. As
much as 50% decline in concentration from Cmax was observed prior to
the end
of infusion.
I'd appreciate any insights concerning the potential mechanisms
underlying
such behavior.
Best regards,
JP Zhang, Ph.D.
Gemin X, Inc.
Email: jzhang.-at-.geminx.com
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The following message was posted to: PharmPK
Dear Jang,
How does the profile of your compound look like after a single dose? If
the drug exhibits multi-exponential concentration-time course, what you
observe in your infusion study might be due to a "distribution" phase of
the drug kinetics. If you continue the infusion long enough, you will
most probably observe pseudo-steady state concentrations later on.
If you have gathered good data after different single doses of your
compound, you might want to consider the following: apply a PK model to
the multiple single dose data and then simulate what would happen if you
gave an infusion similar to what you have tested (next time, preferably
before you do the infusion study :-) ). As long as you are not violating
the model assumptions in your simulation, there should be no surprises
in your actual study.
Toufigh Gordi
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Copyright 1995-2010 David W. A. Bourne (david@boomer.org)