1 reply to this topic

[raghava choudary]

Dear All,

 

How to estimate / model whether a drug is following a zero order absorption ?

 

Plz help me with an example model.........

 

Thanks in advance,

 

Raghav

[Simon Davis]

Hi Raghav, typically I find this when a simple absorption model fails to describe the data well, even if I add a Tlag;  e.g. try fitting the following data with a 1 compartment model and First order absorption.

 

  Here in the Linear plot you see Cmax (orTmax) is not captured well by the built in model PK4.

 

Here's the Semi-log plot for comparison; note that elmination seems off too

 

And finally a user written model that describes the whole curve much better

 

Parameter    Estimate    Units    Stderr    CV%
tvV               96.135         L     9.5470414    9.9308695
tvKe          0.466347      1/h    0.0549163    11.775845
zrate          4399.97      ug/h    200.89798    4.5658944
stdev0        5.38137                1.0983624    20.410461
 

  Simon.

 

PS This example comes from this text book http://www.certara.com/pk-pd-textbook and is covered in our Intro to Phoenix WinNonlin course should you get the opportunity to attend one of those;

 

https://www.certara.com/training or in India/SE Asia contact Venkateswari Muthukrishnan <Venkateswari.Muthukrishnan@certara.com> directly.

Attached Files

•  PK3.xls   6KB   536 downloads

Edited by Simon Davis, 25 November 2014 - 11:49 AM.