NONMEM Users Network Archive

Hosted by Cognigen

RE: Weibull distribution

From: Steve Troy <stroy>
Date: Wed, 11 Apr 2007 10:02:03 -0400

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

-----Original Message-----
From: owner-nmusers
On Behalf Of Khaled Mohammed Abduljalil
Sent: Wednesday, April 11, 2007 9:15 AM
To: nmusers
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
************************************************************
The contents of this message are intended only for the use
of the individual to which they are addressed and may
contain confidential or privileged information. If you are
not the intended recipient, you are hereby notified that
any use, distribution, disclosure or copying of this
message, any attachment or the information contained
therein is strictly prohibited. If you have received this
transmission in error, please notify the original sender
immediately and delete all copies of this message, along
with any attachments. Thank you.
************************************************************

Received on Wed Apr 11 2007 - 10:02:03 EDT

The NONMEM Users Network is maintained by ICON plc. Requests to subscribe to the network should be sent to: nmusers-request@iconplc.com.

Once subscribed, you may contribute to the discussion by emailing: nmusers@globomaxnm.com.