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Re: [NMusers] Why should we avoid using micro rate constants?

From: David at Boomer <>
Date: Sun, 3 Feb 2019 21:24:14 -0700


As mentioned it may have found a local minimum with the micro constants. =
You could try with different starting values and/or limits.

You might also convert the CL/V constants to k12/k21/kel/v1 and see how =
they compare, use them as initial estimates. I seem to remember the =
equations for conversion between parameter types in one of the NONMEM =

David Bourne

> On Feb 3, 2019, at 1:44 PM, Singla, Sumeet K <> =
> Hello everyone!
> I have a question. I was trying to build a 2-compartment PK model for =
marijuana use in occasional and chronic smokers. Initially, I was using =
providing rate constants K12 and K21 ­in PK block and it resulted =
in poor fitting. Then, I later changed to CL,V1, V2 , Q and it resulted =
in proper fitting. I was perplexed as to why I couldn’t get a =
proper fit by providing rate constants? I tried to look online but =
couldn’t find any proper explanation about when (or not) we =
should use micro constants in PK block to define our model in NONMEM? =
Does anyone has any useful insights into this?
> Regards,
> Sumeet Singla
> Graduate Student
> Dpt. of Pharmaceutics & Translational Therapeutics
> College of Pharmacy- University of Iowa

Received on Sun Feb 03 2019 - 23:24:14 EST

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