Dear All, I have a question regarding the explicit usage of a „dose“ in a PML script. A second question regards controlling of the time parameter. I am trying to set up transit compartments in Phoenix/NLME to model delayed drug absorption for a Pop-PK model of a once daily dosed small molecule drug. I would like to code it according to Savic et al. (2007), where the number of transit compartments is a estimated parameter. The key equation reads: dA1/dt = Dose x F x ktr x (Ktr x t)**n x exp(-ktr x t)/n! - Ka x A1 with ktr = transit rate constant, n is number of transit compartments and n! is approximated by Sterling’s formula. How can I implement an explicit dose - as it appears in the above equation - in the PML script? In order to consider multiple dosing in this model one needs to implement a relative time, something like (ktr x (t – tdose))**n., so that time is reset to zero a the next dose. How can this be done in Phoenix/NLME? I think it could be achieved using the reset flag but I am not sure how to do this correctly. I was able to run the model in WinNonLin for single PK profiles, a NONMEM code for this model can be found as a free supplement to Savic et al. paper. For sake of clarity I include the relevant parts of the NONMEM code. Thanks for your comments Roland ;—Setup for multidose transit compartment IF (NEWIND.NE.2) THEN ; beginning of dataset, or new individual TNXD = TIME ; TIME will be the time of the first record of that subject even if it’s not a dose, but PNXD = AMT ; the amount will be 0 if the first record is not a dose ENDIF TDOS = TNXD PD = PNXD IF(AMT.GT.0) THEN TNXD=TIME PNXD=AMT ENDIF ;—Transit compartment KTR =(NN+1)/MTT ;ktr as function of mean transition time MTT F1 = 0 L = 0.9189385+(NN+.5)LOG(NN)-NN+LOG(1+1/(12NN)) ; logarithm of the approximation to the gamma function LBPD = LOG(BIOPNXD) LKTR = LOG(KTR) PFUNC = LBPD+LKTR-L $DES TEMPO = T-TDOS ; time after dose IF(TEMPO.GT.0)THEN KTT = KTRTEMPO DADT(1) = EXP(PFUNC+NNLOG(KTT)-KTT)-KTRA(1) ; dapagliflozin absorption ELSE DADT(1)=0 ENDIF DADT(2) = KTRA(1) - K26A(2) - K23A(2) + K32A(3) -K24A(2) - K20A(2) ;