Help: oral and ig bioavailability by NONMEM

From: Weijiang Zhang <ZHANGW@mail.rx.uga.edu> Subject: Help: oral and ig bioavailability by NONMEM Date: Tue, 28 Aug 2001 02:46:10 GMT Dear NONMEM users: When I tried to use NONMEM to analyze my data, there is a problem I don't know how to do with it. My study is about giving a compound to six subjects by three different administration routes: iv, ig and oral. I used subroutines ADVAN4 TRANS3, that's two compartment with first order absorption. Everything works out fine except the bioavailability. Following is my code for absorption rate (KA)(the absorption is rapid for both routes) and bioavailability: $PK X1=0 X2=0 IF (WZ.EQ.1) THEN ;WZ is the indicator, WZ=1, oral dose X1=1 ENDIF IF(WZ.EQ.2) THEN ;WZ=2, ig dose X2=1 ENDIF KA = X1*THETA(5) + X2*THETA(6) TVF1 = X1*THETA(7) + X2*THETA(8) F1=TVF1 *(1+X1*ETA(2)+X2*ETA(3)) + (1-X1-X2)*THETA(9) Most parameters are well estimated, however, the F1 for oral (theta7) was estimated to be 1.52, for ig (theta8) was 0.58, which were very different from the number (0.95 and 0.70) I got by noncompartmental analysis using Winnonlin. I've already double checked my data set to make sure it's correct. My first question is: Is that right to use F1 here? or F2? Second: Is my code correct to estimate bioavailability for oral and ig in this model? What can I do to get the "right" estimation? Any help will be highly appreciated. Thank you so much for your time and attention. Sincerely, Weijiang Zhang UGA