Dear All, I'm working on the population pharmacokinetics of a mAb, in this study 4 dose levels (50, 100, 200 and 400 mg) were evaluated. I tested different models, but none of them fit well; that's why I decided to find for each dose level the best model. I found the two lower dose levels fitted to Michaelis Menten + CL linear model and the two higher dose levels fitted to QSS Rtot model. I think if I use this code, I'll find the best model for my data, so I appreaciate your suggestions:
$PK TVCL= THETA(1) TVV1= THETA(2) TVQ = THETA(3) TVV2 = THETA (4) TVKM = 0 TVVM = 0 IF(DOS.LT.200) THEN TVKM = THETA (5) TVVM = THETA (6) TVKSS = 0 TVKINT = 0 TVKDEG = 0 TVRMAX = 0 IF(DOS.GT.100) THEN TVKSS = THETA (7) TVKKINT = THETA(8) TVRMAX = THETA(9) ENDIF K = CL/V1 K12 = Q/V1 K21 = Q/V2 S1 = V1 ;---------------------------------- $DES CONC=0.5*(A(1)/V1-RMAX-KSS)+0.5*SQRT((A(1)/V1-RMAX-KSS)**2+4*KSS*A(1)/V1) DADT(1) = -(K+K12)*CONC*V1+K21*A(2)-KINT*RMAX*CONC*V1/(KSS+CONC)-VM*CONC*V1/(KM+CONC) DADT(2) = K12*CONC*V1-K21*A(2) Thank you, Regards, Niurys de Castro -- MSc Niurys de Castro Suárez Profesor Asistente Farmacometría Investigador Agregado Departamento Farmacia Instituto de Farmacia y Alimentos, Universidad de La Habana Cuba
