Re: Why should we avoid using micro rate constants?
You may have found a local minima with the microconstant parameterization.
There generally isn’t any rhyme or reason for why one chooses macro or micro
constants. People will argue that the macro model with Q and Vp is more
interpretable than k12 and k21. That, and scaling reasons, are why one might
choose one parameterization over another.
Pete Bonate
Quoted reply history
On Feb 3, 2019, at 2:54 PM, Singla, Sumeet K
<[email protected]<mailto:[email protected]>> wrote:
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