RE: Weibull distribution
Dear Abduljalil,
I am not an expert on using the Weibull distribution for drug
absorption, but I suspect that the value of TIME in the equation for
DADT(1) should represent the elapsed time since the most recent dose.
For example, if dosing occurs at 0, 24, and 48 hours, then the
observation at 25 hours after the start of the study (ie, 1 hour after
the most recent dose) should use TIME=1 hour in the equation for
DADT(1). However, I suspect that TIME=25 hours is being used in the
current problem.
Good luck,
Steve
Quoted reply history
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
On Behalf Of Khaled Mohammed Abduljalil
Sent: Wednesday, April 11, 2007 9:15 AM
To: [email protected]
Subject: [NMusers] Weibull distribution
Dear NONMEM users,
I have tried to study the pk profiles of a drug after
multiple oral dosage regimen of 500mg every 12hr. The
estimation process was well performed with the first dose
(only) using Weibull function. but if i apply the same
control file to the whole data (ie, single dose and
multiple doses), it does not work any more. I can not
detect my error. Could any one tell me where is it?
neither first order nor Mich.-Menten models fitted the
data like weibull model.
thank you very much in advance for your response.
sincerely yours
Abduljalil
$SUBROUTINES ADVAN6 TRANS1 TOL=3
$MODEL
COMP=(DEPOT,DEFDOSE)
COMP=(CENTRAL,DEFOBS)
$PK
CL=THETA(1)*EXP(ETA(1))
V=THETA(2)*EXP(ETA(2))
BETA=THETA(3)*EXP(ETA(3))
ALPHA=THETA(4)*EXP(ETA(4))
K=CL/V
S1=1
S2=V
$ERROR
DEL=0
IF(F.EQ.0) DEL=0.001
W=F
IPRED=F
IRES=DV-IPRED
IWRES=IRES/(W+DEL)
Y=F+EPS(1)
$DES
DADT(1)=-A(1)*(BETA/ALPHA)*((TIME/ALPHA)**(BETA-1))*EXP(-(TIME/ALPHA)**B
ETA)
DADT(2)=-DADT(1)-A(2)*K
$THETA
(0.01,17,80);
(10,115,900);
(0.1,2.2,30)
(0.1,2.6,30)
(0.001,2)
(0.001,1)
$OMEGA
0.1 0.2 0.08 0.2
$SIGMA
0.2
$EST METHOD=1 INTER PRINT=5 NOABORT MAXEVAL=9999
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