NONMEM Users Network Archive

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RE: Why should we avoid using micro rate constants?

From: janet.wade
Date: Tue, 5 Feb 2019 06:51:05 -0000

Hi All,


It could also be the statistical model. If you are estimating 4 =
parameters then different parameterisations should be fairly equivalent =
if a BLOCK(4) structure is used for both parameterisations. If only the =
diagonal option is used, then this could be why different =
results/minimisations are obtained for different parameterisations.


Kind regards,




Janet R Wade, PhD

Senior Consultant




From: owner-nmusers
Behalf Of Leonid Gibiansky
Sent: 04 February 2019 07:30
To: Singla, Sumeet K <sumeet-singla
Cc: nmusers
Subject: Re: [NMusers] Why should we avoid using micro rate constants?


It could be just coding error, could you show the control stream?



On Feb 3, 2019, at 12:44 PM, Singla, Sumeet K <sumeet-singla

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?



Sumeet Singla

Graduate Student

Dpt. of Pharmaceutics & Translational Therapeutics

College of Pharmacy- University of Iowa


Received on Tue Feb 05 2019 - 01:51:05 EST

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