From: "Liao, Sam [PRI]" <SLIAO@prius.jnj.com>
Subject: RE: centering / maximum function evals
Date: Thu, 22 Jun 2000 19:27:14 -0400

Dear Alison:

I have a PK/PD model in NONMEM that had exceeded the max no. of evaluations of differential equations, 100000 after 30 iterations. Yet,it continued for 54 iteration before it converged. The final parameters does not look reasonalbe to me. How can I increase the maxi no.? I have 3 DE in my PK/PD model and 30 patients each has 28 daily dosing. I think it may be caused by the long treatment period.

Sam Liao


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Date: Fri, 23 Jun 2000 08:54:16 -0400 (EDT)
From: "Jogarao Gobburu 301-594-5354 FAX 301-480-3212" <GOBBURUJ@cder.fda.gov>
Subject: Re: centering / maximum function evals

Dear Sam,
1. The following verbatim code should be of help to you:
$PK
"FIRST
"COMMON/PRCOMG/IDUM1,IDUM2,IMAX,IDUM4,IDUM5
"INTEGER IDUM1,IDUM2,IMAX,IDUM4,IDUM5
"IMAX=200000
...

The constant 200000 gives you twice the default.

2. Usually in my experience performing some simulations to check your equations and initial estimates should be of help. Try that if you have not. Also, of help will be fitting one or two subjects with OMEGAs fixed to zero, if your data permits. Very rarely you need the above code.

Regards,
Joga Gobburu,
Pharmacometrics,
CDER, FDA.