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Dear All,
I am looking for the appropriate equation to calculate clearance. The
subjects are to be administered a bolus IV dose (8 mg/kg or 16 mg/kg)
followed by a continuous infusion (47.5 mg/kg/12 hr or 32 mg/kg/12).
Thanks,
Kathryn Roupe, Ph.D.
Senior Pharmacokineticist
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The following message was posted to: PharmPK
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Check in a first course in Pharmacpkinetics and Biopharmaceutics by
Proff. David Bourne
[Thanks Sidney, that would be http://www.boomer.org/c/p4/ or http://
www.boomer.org/c/p3/
Actually it's a little more complicated. Do you start the infusion at
the same time as the bolus is given? Is there a delay? After just a
bolus dose, clearance can be calculated as Dose/AUC (http://
www.boomer.org/c/p4/c04/c0410.html). During an infusion at steady
state, clearance can be calculated as Infusion Rate/Cp(ss) (http://
www.boomer.org/c/p4/c06/c0602.html). If your objective is to dose to
steady state using a bolus/infusion regimen then the second equation
may be suitable once you have verified that steady state has been
achieved (http://www.boomer.org/c/p4/c06/c0604.html). Otherwise, if
you have enough suitable data points modeling the data in terms of V
and CL should work - db]
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Kate,
Your question is suprisingly odd... almost as if part of your
question is missing. Does this drug undergo (or is expected to
undergo) nonlinear disposition processes, which is why you mentioned
the dose regimen? One assumes you have limited data (i.e. no iv
bolus regimens), and if so, you need only your concentration at
steady state to arrive at a clinical estimate for clearance. It is
not likely you have clinical data without a rough estimate of your
half-life, and so wait at least 5 half-lives use the concentration to
arrive at a preliminary estimate of clearance. Again, one assumes
there is more to the question.
Keep in touch..
-Shawn
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