Re: Dilemma with PPK parameters
Hi Varsha,
Continuing on Ken's response, have you tried a simple model without any
covariates? Do you get the same values
for CL as you do with the control stream you provided? Could you also provide
the
values for all the four THETAs you estimate in your control stream?
Toufigh
On Fri 02/05/10 8:58 AM , "Varsha Mehta" [email protected] sent:
> Dear Group:
> I am seeking some help to logically explain the difference in CL of
> a drug between 2 groups who received the same drug for the same
> indication but one group had induced hypothermia (treatment-N=24)
> while the other did not (control-N=115).
> The half life for control- 111hrs and treatment 129 hrs (roughly)-
> not statistically different.
> However, the parameters:
> Control Group Treatment group
> CL- 0.000105 L/kg/hr (suspect) CL- 0.00467 L/kg/hr
> Vd -0.733 L/kg Vd 0.876 L/Kg
>
> I used the same model for both groups and the half life calc was
> part of the model. I have run the model for both multiple times using
> various theta values. each time the minimization is complete. The
> bootstrap for treatment group gives reasonably good agreement. The
> bootstrap for control parameters match well for Cl (0.000273
> L/kg/hr) but not for Vd (0.416 L/kg).
> Given the relationship between Vd and CL how is this possible? How
> can the half life be so close when there is such a huge difference in
> CL for both groups? Where am I going wrong?
> Would appreciate any help anyone can provide.
> Thanks!!
> Varsha Mehta, MS(CRDSA), Pharm.D., FCCP
> Clinical Associate Professor
> Pharmacy, Pediatrics and Communicable Diseases
> Clinical Pharmacist Neonatal Critical Care
> University of Michigan
> (O) 734-936-8985
> (F) 734-936-6946
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