IV Infusion Pre-Dose Removal

Phoenix Certara Forums Phoenix WNL basics
1

Hello, simple question, for calculating NCA with IV Infusion route, should the pre-dose timepoint be removed, similar to if calculating IV Bolus?
Infusion was 1 hour and first post dose time point is 1 hour.

2

Hi CTUK, this should not be necessary as an infusion curve does not need to be back-extrapolated to Time Zero to give a good estimate of Czero as an IV bolus does. If you tell WinNonlin that there is an observed concentration at time zero that is used regardless of route; if it is empty (or missing) it is calculated as being zero for iv infusion and extravascular.

So you can see it is only for IV bolus you shoudl be careful not to give a concentration of zero at time zero that conflicts PK theory of instant and complete mixing.

Simon.

3

Thanks Simon, that is very clear and very useful!