Hi all,
I am trying to fit a model into a food study PK. This is a cross over study so each subject administered the drug under both fasted and fed state. The drug absorption delayed in fed state (see fig below). The model can fit both fed ONLY and fasted ONLY data very well. However, in the combined dataset, see IPRED vs DV, there are always several data points out of the line. These data are mainly fed state data at the beginning of the absoprtion phase and the delay is not well captured.
So I tried a few modification, set covariate in Ka and Tlag (m09), write code for both fasted and fed Ka and Tlag (m10, so I can give better initial value), and also since fed state seems to fit fine with one cmt, I set flag to make 2 cmt for fasted and 1 cmt for fed. However, the fitting is still not very idea with the combined data.
I would prefer to fit one model for the whole dataset. For fasted state, it is clearly a quick abosrption for 1 cmt and a slow for the 2nd cmt, while for fed state, it is a delay and then a slow 1 cmt. The elimination phase looks quite similar so I think it could fit into one model.
Do you have any suggestions?
For the figure, 1 for fasted and 2 for fed state