NONMEM Users Network Archive

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Re: modeling the circadian baseline

From: Nick Holford <n.holford>
Date: Fri, 27 Apr 2007 18:30:31 +1200

Ying,

If you assign the ETA to a variable outside $DES then you can use the variable in $DES e.g.

$PK

ETAT=ETA() ; ETA for random effect on offset in cycle

$DES

DPS2 = (KOUT*A1 + B1*DPI/12)*DCOS(DPI*(T+ETAT)/12)

I would also suggest putting DPI = 3.14159 in $PK. There is no need to do this assignment every time the differential equation solver is called.

Nick

Ying HONG wrote:
>
> Dear NM users,
>
> A biomarker, which shows clear circadian rhythm during placebo
> treatment, was described by a turnover model with the introduction of a
> periodic time-dependent production function KST with two harmonics. The
> code in $DES is written as follows:
>
> $DES
>
> DPI = 3.14159
> DPS1 = KOUT*A0
> DPS2 = (KOUT*A1 + B1*DPI/12)*DCOS(DPI*T/12)
> DPS3 = (KOUT*B1 - A1*DPI/12)*DSIN(DPI*T/12)
> DPS4 = (KOUT*A2 + B2*DPI/6) *DCOS(DPI*T/6)
> DPS5 = (KOUT*B2 - A2*DPI/6) *DSIN(DPI*T/6)
>
> KST = DPS1 + DPS2 + DPS3 + DPS4 + DPS5
>
> DADT(1) = KST - KOUT*A(1)
>
> In the paper published by Hempel et al (CPT, 1998;64:622-35), a ETA was
> introduced in the time T which accounts for the differences in wake-up
> times between subjects (e.g. DCOS(DPI*(T+ETA)/12). Because ETA is
> prohibited in the $DES, how can I code the interindividual variability
> of time in the control stream?
>
> Any suggestion is highly appreciated!
>
> Kind Regards, Ying
>
> --
> Ying HONG, PhD
> Department of Pharmaceutical Sciences
> University at Buffalo, SUNY
> C237 Cooke Hall, Buffalo, NY 14260
>
> Tel: 716 645 2828 ext 275
> Fax: 716 645 3693
> E-mail: yhong6

--
Nick Holford, Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand
email:n.holford
http://www.health.auckland.ac.nz/pharmacology/staff/nholford/
Received on Fri Apr 27 2007 - 02:30:31 EDT

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