Implementation of equivalence of RATE-2 in NONMEM: Estimation of dur

What would you like Pmetrics to do in the future?
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tbouillon
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Implementation of equivalence of RATE-2 in NONMEM: Estimation of dur

Post by tbouillon » Fri Oct 14, 2016 10:11 pm

Dear Colleagues
I would like to politely request the option to estimate the duration of a 0 order input.
NONMEM: RATE=-2
This gives you addl. flexibility in your input models (sequential or parallel 0 and 1st order process) and might save you from having to go to differential equations.
I deliberately use the reference to NONMEM in my post, because NONMEM is regarded as Gold Standard in pharmacometrics. A lot of pharmacometricians start with NONMEM and may then consider other options. So, they will inherently make a comparison between NONMEM and their new love. I run both NONMEM and Pmetrics on my machine, focusing on Pmetrics since version 1.5 came out (24.5.2016 :)).
Best regards and please keep Pmetrics growing.
Thomas

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mneely
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Re: Implementation of equivalence of RATE-2 in NONMEM: Estimation of dur

Post by mneely » Sun Oct 16, 2016 1:52 pm

Hi Thomas,

Could you give an example of when you would want to do this?

Thanks very much.

tbouillon
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Joined: Sun Feb 22, 2015 11:51 pm
Location: Switzerland

Re: Implementation of equivalence of RATE-2 in NONMEM: Estimation of dur

Post by tbouillon » Mon Oct 17, 2016 2:03 am

Hi Michael

Well, anytime you are exploring different input models (there is more to life than ka):

standard suspects:
1st order
0 order
sequential 0 and then first order ("infusion" into depot, 1st order from there to central).
parallel 0 and first order (concomitant "infusion" into central compartment and bolus into depot compartment with 1st order transfer into central, needs 2 doses and 2 F terms, which partition the doses #Pri F1, #Sec F2=1-F1)

These need no #Dif block (so you don't need a cluster or supercomputer :))

Transit compartment model (Savic, Wilkins, Karlsson):
Stirling approximation to estimate number of compartments, #Dif mandatory

I know this is not exhaustive, but this is what I usually tried in the past.
Best regards
Thomas

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