NONMEM Users Network Archive

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Re: Steady state model

From: Nick Holford <n.holford>
Date: Thu, 06 Aug 2009 07:44:00 +1200


I dont understand exactly how NONMEM computes the steady state value but
with ODEs it seems to be done using a numerical root finding procedure
i.e. solves for the amt in each of the compartments when all the DEs
have a value of zero.

The amt in each compartment is set to the steady state value. There is
no initial 'parameter' for the compartment. Compartment amounts are
variables. Parameters are constants. Parameters (e.g. THETA values) are
used in the ODEs to define the DE values.

Perhaps Alison Boechmann (who wrote the code) could give a more thorough


Sherwin K Sy wrote:
> Dear NONMEM users,
> I'm wondering what equation or ODE is used in NONMEM when the steady
> state is set (i.e. SS = 1). Is it the case that the initial parameter
> for the compartment is set to a different value? If so, how does
> NONMEM set this value?
> I would appreciate if anyone can provide me with a reference or point
> me to where I can find this information, including the type of
> equation used for extravascular, iv bolus and iv infusion models.
> Thanks,
> Sherwin

Nick Holford, Professor Clinical Pharmacology
Dept Pharmacology & Clinical Pharmacology
University of Auckland, 85 Park Rd, Private Bag 92019, Auckland, New Zealand
mobile: +64 21 46 23 53
Received on Wed Aug 05 2009 - 15:44:00 EDT

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