Hi all,
How to generate secondary parameters for a 2 compartment model using phoenix Model??
Thanks in advance...
Raghav
Posted 29 August 2015 - 10:02 AM
Hi Raghav, a simple way to get started when using standard library/built in models is to the use the set_WNL_model button and you will notice this populates the secondary parameters.
If you need more, or you are creating a new model this is where you add the formula for that secondary parameter.
Simon
Posted 29 August 2015 - 12:59 PM
PK Modeling 290815.phxproj 447.98KB 376 downloads
Hi Simon,
Thank you for the reply,
Used the Set_WNL Model and a set of secondary parameters were generated. However some parameters that are related to 3 comp were also added. The standard errors and % CV are high.
In theta tab for some estimates the 95 % CI includes negative values ???
Regards,
Raghav
Posted 29 August 2015 - 09:01 PM
Raghav, when changing models I would generally recommend choosing 'replace' so that you don't 'keep' parameters which are no longer relevant to the new model as you seem to have done in this case.
otherwise I might be tempted to consider some modifcation to the model e.g. zero-order absorption?
Simon.
Posted 02 September 2015 - 12:33 PM
Raghav,
Another option if you want to avoid negative values is to transform your parameter in the log domain. For example
Cllog =log(Cl)
In the model you will have Cl replaced by exp(Cllog)
You will get 'raw' confidence intervals for Cllog that can be negative then exponentiate it and they will be positive.
Simon.
Posted 03 September 2015 - 04:38 AM
Raghav,
Another option if you want to avoid negative values is to transform your parameter in the log domain. For example
Cllog =log(Cl)
In the model you will have Cl replaced by exp(Cllog)
You will get 'raw' confidence intervals for Cllog that can be negative then exponentiate it and they will be positive.
Si
Raghav, when changing models I would generally recommend choosing 'replace' so that you don't 'keep' parameters which are no longer relevant to the new model as you seem to have done in this case.
otherwise I might be tempted to consider some modifcation to the model e.g. zero-order absorption?
Simon.
Hi Simon,
Considered 2 compartment , Zero order absorption model and still see that the precision on parameters V2 and CL2 is very low (high % CV) !!
Am i missing anything , plz find the attached model. PK Modeling 290815.phxproj 1.07MB 374 downloads
How can i get secondary parameters when Editing Graphically the model.
thanks in advance ,
Raghav
Posted 03 September 2015 - 10:23 AM
Hi Raghav, secondary parameters can be added in Graphical model the same way as in Built-in/library model mode like before. Remember if starting from a built-in model you'll need to check that edits you've made to the model don't make the calculation formulas invalid for any existing secondary parameters.
Regarding the higher CV% of V2 etc, this may just be an identifiability issue as you are not directly observing this compartment but I'll ask a colleague if he has any other suggestions.
Simon.
Posted 05 September 2015 - 10:39 AM
Hi Raghav, secondary parameters can be added in Graphical model the same way as in Built-in/library model mode like before. Remember if starting from a built-in model you'll need to check that edits you've made to the model don't make the calculation formulas invalid for any existing secondary parameters.
Regarding the higher CV% of V2 etc, this may just be an identifiability issue as you are not directly observing this compartment but I'll ask a colleague if he has any other suggestions.
Simon.
Raghav, when changing models I would generally recommend choosing 'replace' so that you don't 'keep' parameters which are no longer relevant to the new model as you seem to have done in this case.
otherwise I might be tempted to consider some modifcation to the model e.g. zero-order absorption?
Simon.
Hi All,
I have a general question on Zero order absorption. If a compound follows zero order absorption and has lag time (say for e.g., 1 hr), will the tmax change upon increasing the doses ?? Will Cmax increase proportionately to initial dose ??
How they are comparable with respect to first order absorption ?
Best regards,
Raghav,
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