Dear Leonid, Thanks for yor suggestion. I've never thought in that possibility. However, I have two questions: 1-Why must I write those equations inside $DES? 2-Do you think the ODE that I proposed are Ok?
Thank you very much MSc Niurys de Castro Suárez Assistant Professor of Pharmacometrics Assistant Research Pharmacy Department Institute of Pharmacy and Food, University of Havana Cuba El 22/07/2021 16:04, "Leonid Gibiansky" <lgibian...@quantpharm.com> escribió: > Definition of CL should be moved inside the DES block; other than that, > looks fine: > ;---- DES ------ > $DES > CL2_TIME = CL2*EXP(-KDES*T) > CL_TOTAL = CL2_TIME + CL1 ; total clearance > ... > > Thanks > Leonid > > > On 7/22/2021 3:30 PM, Niurys.CS wrote: > >> Dear nmusers, >> I'm working on the pharmacokinetics of an antiCD20 mAb; I suspect the >> clearance of this mAb should be time dependent as rituximab’s clearance do. >> I tried to model this behavior but I’m not sure if the ODEs are correct. >> Please can you help? I share part of the code. >> >> $SUBROUTINE ADVAN13 TOL=9 >> $MODEL COMP=(CENTRAL) COMP=(PERIPH1) >> $PK >> ;---- STRUCTURAL PARAMETERS ------ >> TVCL1 = THETA(2) ; system-nonspecific clearance >> TVV1 = THETA(3) >> TVQ = THETA(4) >> TVV2 = THETA(5) >> TVKDES = THETA(6) ; rate constant of the specific clearance decay >> TVCL2 = THETA(7) ; time varying clearance at time zero >> ;---- MU_TRANSFORMATION ------ >> MU_1 = LOG(TVCL1) >> MU_2 = LOG(TVV1) >> MU_3 = LOG(TVQ) >> MU_4 = LOG(TVV2) >> MU_5 = LOG(TVKDES) >> MU_6 = LOG(TVCL2) >> ;---- INDIVIDUAL PARAMETERS ------ >> CL1 = EXP(MU_1+ETA(1)) >> V1 = EXP(MU_2+ETA(2)) >> Q = EXP(MU_3+ETA(3)) >> V2 = EXP(MU_4+ETA(4)) >> KDES = EXP(MU_5+ETA(5)) >> CL2 = EXP(MU_6+ETA(6)) >> S1 = V1 >> ;---- INITIAL CONDITIONS ------ >> A_0(1) = 0 >> A_0(2) = 0 >> CL2_TIME = CL2*EXP((-KDES)*(TIME)) >> CL_TOTAL = CL2_TIME + CL1 ; total clearance >> ;---- DES ------ >> $DES >> CONC = A(1)/V1 >> DADT(1) =-(CL_TOTAL/V1)*A(1)-(Q/V1)*A(1)+(Q/V2)*A(2) >> DADT(2) = (Q/V1)*A(1)-(Q/V2)*A(2) >> ;----$ERROR ------ >> CONC1 = A(1)/V1 >> IPRED=-3 >> IF(CONC1.GT.0) IPRED=LOG(CONC1) >> W = THETA(1) >> Y = IPRED+W*EPS(1) >> IRES=DV-IPRED >> IWRES=IRES/W >> >> Thank you, >> Niurys >> >> MSc Niurys de Castro Suárez >> Assistant Professor of Pharmacometrics >> Assistant Research >> Pharmacy Department >> Institute of Pharmacy and Food, >> University of Havana >> Cuba >> >>
