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: [email protected]<mailto:[email protected]> /
[email protected]<mailto:[email protected]> Mobile: +31 659738693
Inherit past calculation of parameter in NONMEM
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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[email protected]
www.pharmetheus.com
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Quoted reply history
On 14 Jun 2017, at 11:35, Guo, Tingjie <[email protected]> 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: [email protected] / [email protected] Mobile: +31 659738693
Tingie,
You can "remember" the value of any variable created in NM-TRAN abbreviated code. You have to be careful if the variable is a random effect to always include the else case.
e.g.
IF (NEWIND.LE.1) THEN
CLLAST=? ; some plausible initial value
ENDIF
IF (CL.LE.0) THEN
CL=CLLAST
ELSE
CL=CL
ENDIF
CLLAST=CL
Best wishes,
Nick
Quoted reply history
On 14-Jun-17 11:35, Guo, Tingjie 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: [email protected] < mailto: [email protected] > / [email protected] < mailto: [email protected] > Mobile: +31 659738693
--
Nick Holford, Professor Clinical Pharmacology
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