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Re: [NMusers] Estimation of Intake Time

From: Sven Mensing <sv.mensing_at_gmail.com>
Date: Thu, 18 Jun 2015 16:48:36 +0200

Hi Andrzej,

you could add 12h to each of your observation times (leave dosing times as
is).
In NONMEM you'd do something like

TimeShift=12
IF(FLAG_AM.EQ.1) TimeShift=12 * 1/(1+EXP(THETA(17))) ;ensure TimeShift is
in between 0 and 12
ALAG1=TimeShift

If you want to go all the way, you could extend this with IOV or similar...

Kind regards

Sven Mensing

2015-06-18 15:35 GMT+02:00 Andrzej Bienczak <andrzej.bienczak_at_googlemail.com
>:

> Dear NMusers,
>
>
>
> I would like to present you with a problem that some of you might have
> faced before. I am currently building a PK model for a drug with once daily
> oral administration. The drug has a long half-life and can be taken either
> in the morning or at night. Unfortunately due to lack of consistency in the
> recording of the administration times by the study team part of the
> patients flagged to have taken the medication in the mornings were in fact
> taking it at night (i.e. 08:25 corresponds to 20:25 the previous day). At
> this stage there is no way of tracking back what the correct intake times
> were.
>
>
>
> The data consists of 2 sparse measurements per patient and indeed looking
> at individual profiles you can clearly see that some samples are from the
> elimination phase, indicating the drug was taken more than 12h prior. I
> could correct the dataset based on an empirical judgement backed up by the
> visual analysis but I was hoping there would be a more robust way.
>
>
>
> Is there any way to put a THETA on the dosage time for those patients to
> let NONMEM estimate a corrected administration time?
>
>
>
> I tried simply adding an extra parameter on the intake time for those
> patients (placed the code in $PK):
>
> IF(FLAG_AM.EQ.1) TIME=TIME-THETA(17)
>
>
>
> But received the following error message:
>
>
>
> AN ERROR WAS FOUND IN THE CONTROL STATEMENTS.
>
> AN ERROR WAS FOUND ON LINE 30 AT THE APPROXIMATE POSITION NOTED:
>
> IF(FLAG_AM.EQ.1) TIME=TIME-THETA(17)
>
> X
>
> THE CHARACTERS IN ERROR ARE: TIME
>
> 236 DATA ITEM MAY NOT BE CHANGED WITH THIS VALUE OF ICALL.
>
>
>
>
>
> I would be grateful for some suggestions on how to deal with this issue.
>
>
>
> Regards,
>
>
>
> Andrzej
>
>
>
>
>
> Andrzej Bienczak
>
> MSc, MPharm, DiplPharm
>
> Pharmacometrics Group
>
> Division of Clinical Pharmacology
>
> Department of Medicine
>
> University of Cape Town
>
>
>
>
>

Received on Thu Jun 18 2015 - 10:48:36 EDT

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