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Re: scaling problem??

From: Leonid Gibiansky <LGibiansky>
Date: Fri, 26 Mar 2010 15:20:29 -0400

Hi Varsha
You may use everything in the original variables (dose in mg, conc in
iU/mL) but your parameters will be defined up to the transformation
Fu=iU/mg (amount of iU in each mg).

Without knowing this value, the only thing that you determine from the
data is CL/Fu, V/Fu, etc.

You may explore the analogy between bioavailability and this unit
transformation: if you would know Fu, you could have dose in mg, but use
bioavailability-like parameter F1 =Fu (F2=Fu, etc.) thus transforming
your dose from mg to iU. Since you do not know Fu, it cannot be (similar
to bioavailability, if there is no IV formulation) defined from the data.

So the short answer: no transformation is necessary but all the
parameters will be defined as CL/Fu, V/Fu, etc. It will not interfere
with the group comparison since (CL/Fu)_1/(CL/Fu)_2 = CL_1/CL_2, etc..


Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
e-mail: LGibiansky at
tel: (301) 767 5566

Varsha Mehta wrote:
> Dear Group:
> I hope someone can help me with the following scaling problem.
> I have data on two groups that I would like to compare the PPK estimates on. The drug is dosed in mg (set amount every 12 hours). The plasma level data is for a surrogate marker and is expressed as iU/mL.
> What kind of scaling should one use in the $PK block?
> Thanks in advance.
> Varsha
> Varsha Mehta, MS(CRDSA), Pharm.D., FCCP
> Clinical Associate Professor
> Pharmacy, Pediatrics and Communicable Diseases
> Clinical Pharmacist Neonatal Critical Care
> University of Michigan
> (O) 734-936-8985
> (F) 734-936-6946
> varsham
> **********************************************************
> Electronic Mail is not secure, may not be read every day, and should not be used for urgent or sensitive issues
Received on Fri Mar 26 2010 - 15:20:29 EDT

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