Modeling Cmin and Tmin

Dear NMUser, I am a beginner in NONMEM and I have a question regarding modeling Cmin and Tmin. I have data of a biomarker which decreases after drug intake and I want to determine the minimum change from baseline (Cmin) as well as the corresponding time (Tmin). I tried different models but the estimated values for these parameters are not plausible or always zero. Has someone experience with this or any idea to solve this problem? Thanks a lot Best regards Friederike Attached I send you a part of my code: $SUBROUTINE ADVAN6 TOL=3 ... $DES ... DADT(5) = KIN*INH-KOUT*A(5) ; Biomarker CMT IF(TIME.EQ.0) THEN CMIN = BASE ; Baseline conc also estimated by NM TMIN=0 ENDIF CC=A(5) IF(CC.LT.CMIN) THEN CMIN= CC TMIN= T ENDIF REL = CMIN/BASE ; change relative to baseline ... $ESTIMATION SIG=2 PRINT=1 METHOD=1 INTER MAXEVAL=0 NOABORT Friederike Kanefendt Pharmacist, PhD-Student University of Bonn -Clinical Pharmacy- An der Immenburg 4 D-53121 Bonn Phone: +49 (0)228 73-5781 Fax: +49(0) 228 73-9757 [email protected]