Problem with multiple dose input

From: Michael_Looby@sandwich.pfizer.com Subject: Problem with multiple dose input Date: 22 Oct 1997 12:59:53 -0400 Dear NONMEM users, I would like to alert you to a problem I encountered recently which cost me some time and nerves. I am not sure what is going on, perhaps you may have some ideas..... I was developing a model with simultaneous input into 2 compartments: ------------------------------------------ TIME CON AMT RATE CMT EVID MDV SS ------------------------------------------ 0 0 5000 20000 1 1 1 0 0 0 0 -1 3 1 1 1 0 0 9999 -1 3 1 1 0 ------------------------------------------ The input to compartment 1 is an infusion at time 0, the input to compartment 3 is a steady-state infusion followed by a nonsteady-state infusion both also at time 0 and both of which have their rates estimated. Surprisingly (to me at least) this dosing code did not produce ANY input into either compartment. After much trial and error I discovered that the following dosing code worked. For some reason I had to put the steady-state dose (into CMT 3) before the nonsteady-state doses into CMT 1 (or CMT 3). ------------------------------------------ TIME CON AMT RATE CMT EVID MDV SS ------------------------------------------ 0 0 0 -1 3 1 1 1 0 0 9999 -1 3 1 1 0 0 0 5000 20000 1 1 1 0 ------------------------------------------ For me at least it is not intuitive that doses to different compartments should interfere with each other. I would be interested in hearing your comments. Regards Mick Looby PFIZER CENTRAL RESEARCH