coding data at steady-state

Dear all, I have started working with NONMEM some months ago and I would really appreciate some help from the forum. I am building a monocompartmental model using ADVAN 2 for a drug which is administered every 12 h. The morning dose, in some patients, differ from the evening dose. The plasma samples have been collected after the first dose (i.e. before steady state) and before and after the dose given on day 28 (considered at steady state). I set the data as: #ID OCC EVID TIME SS II AMT DV 8 1 1 0 0 0 500000 8 1 0 0.52 0 311.0 8 1 0 1.0 0 1615.0 8 1 0 1.5 0 2966.8 8 1 0 2.7 0 3923.3 8 1 0 5.92 0 3355.0 8 1 0 7.93 0 2563.7 8 2 1 660 1 24 350000 8 2 1 672 2 24 500000 8 2 0 671.9 2350 8 2 1 684 2 24 333333 8 2 0 672.6 0 2400.0 8 2 0 673.1 0 2780.1 8 2 0 673.67 0 2890.2 8 2 0 675.15 0 4110.0 8 2 0 678.13 0 3440.1 8 2 0 680.12 0 3190.0 I have the following questions: 1- Is the data file set up to correctly account for both the initial (non steady state) dose and concentration time data along with the steady state dose and concentration time data? 2- Does the steady state dosing affect the pre-steady state dose and concentration time data? 3- I can not run the program when just considering the steady-state doses and concentrations. Am I missing something? Thank you very much for your help!!! Paula Schaiquevich, PhD Postdoctoral Research Associate Pharmaceutical Sciences St.Jude Children's Research Hospital 332 North Lauderdale street Memphis, TN 38105 Danny Thomas Research Center Room D1034 Mail Stop 314 Phone: (901)-495-5938 E-mail: [EMAIL PROTECTED]