Re: [NMusers] Inherit past calculation of parameter in NONMEM

From: Jakob Ribbing <jakob.ribbing_at_pharmetheus.com>
Date: Wed, 14 Jun 2017 11:48:24 +0200

Dear Tingjie,

It is possible to create a variable to store the last value, using =
IF-ELSE.
However, more importantly I would suggest not to use functional forms =
for covariate models that allows restricting the typical CL to positive =
values only.
Use a multiplicative parameterization of covariate effects, rather than =
additive - unless you know the additive is more mechanistic, e.g. high =
extraction over two different organs is independent, so that =
multiplicative may be inappropriate if you know the two covariates each =
affect only one of the two (and not the same organ).
Set boundaries to covariate effects so that a covariate may not reduce =
by more than 100%, or use e.g. a power model, if covariate values are =
>0.


Best regards

Jakob



Jakob Ribbing, Ph.D.

Senior Consultant, Pharmetheus AB



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On 14 Jun 2017, at 11:35, Guo, Tingjie <t.guo_at_vumc.nl> wrote:

> Dear NMusers,
>
> Maybe a simple question. I was wondering if there is such =
functionality in NONMEM to inherit the past (e.g. previous row) value of =
parameter calculated with time varying covariates? For instance, the CL =
was determined by a time varying covariate. Calculation CL was a =
negative number in time record 3 due to the covariate value at that time =
point. I would like to use calculation CL in time record 2 as instead =
for time record 3. Pseudocode is somewhat like ‘IF (CL[i].LE.0) =
CL[i]=CL[i-1]’. Is this possible to implement within NONMEM? Thanks =
in advance.
>
> Warm regards,
> Tingjie
>
> Tingjie Guo I Trainee Research Assistant
> Academic Medical Centre, University of Amsterdam.
> VU University Medical Centre, Vrije University Amsterdam.
> Room ZH-7D-172, De Boelelaan 1117, 1081 HV Amsterdam, The Netherlands.
> Email: t.guo_at_amc.uva.nl / t.guo_at_vumc.nl Mobile: +31 659738693



Received on Wed Jun 14 2017 - 05:48:24 EDT

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