Re: Why should we avoid using micro rate constants?
Sumeet
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 manuals.
David Bourne
Quoted reply history
> On Feb 3, 2019, at 1:44 PM, Singla, Sumeet K <[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