Michaelis-Menten model i nonmem
From:Toufigh Gordi
Subject:[NMusers] Michaelis-Menten model i nonmem
Date:Mon, 17 Feb 2003 11:25:39 -0500
Hi!
I am trying to implement a "simple" binding action of a drug in nonmem. The
PK of the drug is characterized (3-comp). The binding is given as %bound
receptors (between 0-100). I have the following coding:
$ERROR
IPRED=F
W=1
IRES=DV-IPRED
IWRES=IRES/W
Y1=IPRED+(IPRED*EPS(1)+EPS(2))*W
Y2=(BMAX*IPRED/(BC50+IPRED))+EPS(3)
Q=1
IF (PKPD.EQ.2) Q=0
Y=Q*Y1+(1-Q)*Y2
All PK parameters (including eps (1) and (2)) are fixed. Altough the model
gives expected estimates of BMAX and BC50, EPS(3) is large (over 300%),
which results in poor individual fits.
Any suggestions?
Toufigh Gordi