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For plasma concentrations of drugs 1 compartment PK models are
usually first order or zero order. There is a WinNonlin model for
first order absorption , 1 compartment model with first order
elimination. Similarly there is a zero order model, 1 compartment
model with first order elimination.
Does anyone have the code for a WinNonlin model for describing mixed
order absorption (first and zero order), 1 compartment model with
first order elimination.
It has occurred to me that some drug formulations may display mixed
order absorption and that plasma concentrations may be best fitted by
such a mixed order model.
I invite comments on above,
Angus McLean
8125 Langport Terrace,
Gaithersburg,
MD20877
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The following message was posted to: PharmPK
Angus,
All absorption models that are based on simple zero or first order
absorption are severe approximations. They'll work for some drugs,
but the
interactions that can occur among such things as regionally dependent
solubility, dissolution rate, precipitation, degradation in the
lumen, and
transporters, for example, are far too complex to be treated properly
with
such simple models. Empirical models can be useful, but mechanistic
models
provide insight.
With today's state-of-the-art tools (GastroPlus(tm), SimCyp(tm), PK-
Sim(tm))
there's no need to oversimplify and perhaps mask the knowledge than
can be
derived from data.
Walt Woltosz
Chairman & CEO
Simulations Plus, Inc. (AMEX: SLP)
42505 10th Street West
Lancaster, CA 93534-7059
U.S.A.
http://www.simulations-plus.com
Phone: (661) 723-7723
FAX: (661) 723-5524
E-mail: walt.-at-.simulations-plus.com
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