Dear All,
I am having a strange issue with my model. I have a dataset after oral
administration and samples are collected on time points 0,1,2,4 and 8 hours at
steady state. I fit this data with ADVAN5 to a 2-comp model. I am getting
volume of peripheral compartment estimated as my initial estimate. Other
parameters are not much changing by changing Peripheral comp. Thinking this is
identifiability issue (probably not), I tried a 1-comp model and the fit was
worse than 2-comp and OBJFUN also much higher than 2-comp model. I tried
several initial estimates of the peripheral volume but doing the same thing. I
appreciate if anybody share some of their experience here.
I am giving my initial estimate in this format: $THETA (0,500);POPVP
Regards,
Ayyappa Chaturvedula
Issue with Volume of Peripheral Comp
Ayyappa
Most likely, this is a coding error, so it would help if you post the code of your model.
Leonid
--------------------------------------
Leonid Gibiansky, Ph.D.
President, QuantPharm LLC
web: www.quantpharm.com
e-mail: LGibiansky at quantpharm.com
tel: (301) 767 5566
Quoted reply history
On 8/16/2010 6:09 PM, Ayyappa Chaturvedula wrote:
> Dear All,
>
> I am having a strange issue with my model. I have a dataset after oral
> administration and samples are collected on time points 0,1,2,4 and 8
> hours at steady state. I fit this data with ADVAN5 to a 2-comp model. I
> am getting volume of peripheral compartment estimated as my initial
> estimate. Other parameters are not much changing by changing Peripheral
> comp. Thinking this is identifiability issue (probably not), I tried a
> 1-comp model and the fit was worse than 2-comp and OBJFUN also much
> higher than 2-comp model. I tried several initial estimates of the
> peripheral volume but doing the same thing. I appreciate if anybody
> share some of their experience here.
>
> I am giving my initial estimate in this format: $THETA (0,500);POPVP
>
> Regards,
> Ayyappa Chaturvedula