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[NMusers] tracer-tracee kinetics

From: Ann Rigby-Jones <>
Date: Wed, 6 May 2015 10:22:43 +0000

Dear NONMEM Users Group

I have been asked to help with modelling saliva concentration data from a t=
racer-tracee study of an endogenous substance. Human volunteers were given =
an oral dose of the labelled tracer substance and a series of saliva sample=
s were collected over the following 24 hours.

* The dependent variable is in the form of a ratio (unitless) of th=
e tracer to tracee (endogenous) saliva concentrations.

* The dose amount (micromoles) and time of dose are known. The dos=
e is given as the oxidised form of the measured compound.

Modelling it as a 2-compartment mammillary model with a depot compartment p=
roduces reasonable plots but of course, the output data is not useful.

My questions are:

1) How does one work with a ratio as a DV and make sense of the output data=

2) Would a metabolite model be a suitable way of dealing with the dose bein=
g in a different chemical form to that measured? Is there a better way?

3) Can anyone guide me towards similar published work?

Grateful for any advice. With thanks and all best wishes


Dr Ann Rigby-Jones
Lecturer in Pharmacology, Anaesthesia Research Group
Plymouth University Peninsula Schools of Medicine & Dentistry

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Received on Wed May 06 2015 - 06:22:43 EDT

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