Re: Estimation of Intake Time

2015-06-18 15:35 GMT+02:00 Andrzej Bienczak <[email protected] >: > 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 > > > > >