Bioequivalence and Bioavailability Forum

Dear VH,
Are you aware there is a forum dedicated to Certara's Phoenix IVIVC software, if you are using this then I suggest you *follow* this forum as you may find several tips and tricks of interest to you.

https://support.certara.com/forums/forum/32-ivivc/

Also I'm not sure if yours is a 'trick' question;

" I am using the IVIVC toolkit for this. Is it possible to have a non-zero value for the input rate at the zero time-point?"

So my question to you is do you have a profile that exhibits this behaviour and if so what happened? Since it's Monday and I'm procrastinating on something else, I just tried this in a project and I see it triggers the following error message;


So moving to the second part

"If yes, when does this happen and how do you interpret it? "

Well I guess you have to consider what this means, you are trying to deconvolve a profile to better understand the absorption process; it's not considered probable that from extravascular dosing you would instantly see drug in the blood stream so here are a few possibilites to consider.

1. endogenous compound or some close analogue, consider a baseline subtraction first but be aware of whether this compound has a constant background level or if it varies e.g. diurnally.
   
   
2. mis-recording of sampling time, e.g it's said to be pre-dose (which is what time zero normally means practically), but in fact was taken after dose administration (could also be they had an issue dosing and mis dosed.
   
   
3. some assay error in lab, perhaps a switched sample.
   
   
4. insufficient washout between dose periods, again you may need to fix this in future treatment periods. For now you may need to extrapolate the elimination from period 1 and subtract from period 2.

Simon.