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[NMusers] DDEs in NONMEM

From: Jonathan Moss <jjmoss_at_btconnect.com>
Date: Mon, 7 Mar 2016 14:34:07 +0000

Dear all,

 

I have a problem regarding delay differential equations (DDEs) in NONMEM. So
far, I have been unable to find a way of successfully using DDEs in NONMEM,
due to there being no in-built DDE solver (as far as I know). To me, it
seems that the problem is that there is no way of recalling the value of the
dependant variable at an earlier time point within the $DES block (u(t-T),
where T is some fixed value, possibly to be estimated). I think that the
problem is not a simple one to solve as NONMEM uses an adaptive step size
when performing the integration, so even if there was a table output of the
past values of the dependant variable, the value at the exact time (u(t-T))
might not exist.

Has anybody been able to successfully implement DDEs in NONMEM? I would
really appreciate some help with this.

 

Note: I am talking about DDEs in a general sense, I know that certain
specific cases of DDEs can be solved in NONMEM (ref: Modelling of delays in
PKPD, classical approaches and a tutorial for delay differential equations,
G Koch, W. Krzyzanski, J. J. Perez-Ruixo, Johannes schropp, JPKPD).

 

Many thanks,

 

Jon Moss, PhD

Modeller

BAST Inc Limited

Loughborough Innovation Centre

Charnwood Wing

Holywell Park

Ashby Road

Loughborough, LE11 3AQ, UK

Tel: +44 (0)1509 222908

 


Received on Mon Mar 07 2016 - 09:34:07 EST

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