Re: Diagnostics
Hi
Some things to consider:
- does your data support non-linear kinetics (perhaps all your actual data are within the "linear" range of your MM kinetics)?
- are your estimates of Vmax and Km correlated?
- what about the estimates of IIV on Vmax and Km? Are they realistic?
Sebastien
fakrudeen ali ahamed wrote:
> Dear All,
>
> I am trying to develop a pop pk model for my data.
> my compound follows MM kinetics.
> Pls find my control stream below.
>
> $PROBLEM Pop pk modeling
> ;UNITS: TIME=h (h),CONCENTRATION=MG/L
> ;Vmax= µg/h, KM = µg/mL, VOLUME = L
> ;DOSE = MG
>
> $DATA Pheny.csv IGNORE=#
>
> $INPUT ID TIME DV MDV DVID AMT WT AGE SEX LFT
>
> $SUBROUTINE ADVAN6 TRANS1 TOL=9
>
> $MODEL
> COMP=CENTRAL
>
> $PK
>
> Vmax=THETA(1)*EXP(ETA(1)) ;MAXIMUM RATE OF ELIMINATION
>
> KM = THETA(2)*EXP(ETA(2)) ;CONC AT 50% Vmax
>
> V =THETA(3)*EXP(ETA(3)) ;VOLUME OF DISTRIBUTION IN L
>
> S1=V
>
> $DES
>
> CP=A(1)/S1
>
> DADT(1)=-Vmax*CP/(KM+CP) ;UNITS OF VMAX = µg/h
>
> $ERROR
>
> Y=F+F*ERR(1)+ERR(2)
> IPRED=F
>
> $THETA (1,5) ;POPVMAX
>
> $THETA (1,2) ;POPKM
>
> $THETA (1,5) ;POPV
>
> $OMEGA 0.04 ;BSVVMAX
>
> $OMEGA 0.04 ;BSVKM
>
> $OMEGA 0.09 ;BSVV
>
> $SIGMA 0.02 ;ERRCV
>
> $SIGMA 0.1 ;ERRSD
>
> $ESTIMATION METHOD=1 INTERACTION MAXEVALS=9990 PRINT=5 POSTHOC
>
> $COVARIANCE MATRIX=S
>
> $TABLE ID AMT TIME DV MDV NOPRINT ONEHEADER FILE=mytab1
> $TABLE ID TIME DV IPRED NOPRINT ONEHEADER FILE=sdtab1
> $TABLE ID TIME DV NOPRINT ONEHEADER FILE=patab1
> $TABLE ID AGE WT AMT NOPRINT ONEHEADER FILE=cotab1
> $TABLE ID NOPRINT ONEHEADER FILE=catab1
>
> The run was successful but am getting some unrealistic km value;also am not able to get the diagnostics plots.
>
> Any guidance or suggestions would be highly appreciated.
>
> Regards
> Dr.N.FAA
>
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