Bioequivalence and Bioavailability Forum

Dear all,
I am using winnonlin v. 6.2 with ivivc toolkit for ivivc,
I want to know how Time scalling parameter calculated in this software also i didn't understand the correlation parameter estimation specified in the manual for eg. Abscale and Tscale etc..initial value or bound should be provided for them..

Why there is need to give the upper bound and lower bound to be given
for Tscale parameter or Tlag?when it can be calculated only from Tvitro vs Tvivo Levy plot BY LINEAR REGRESSION or is it nonlinear regression ,

also can anyone elaborate the correlation model which are provided in
manual some of them as per i understood

(1) Fabs = Diss(Tvivo)

means :- regression between Fabs (amount absorbed at time invivo for given formulations) vs Diss (Tvivo) (amount dissolved at the corresponding invivo time for given formulations)
y=x;
y=amount absorbed at time invivo
x=amount dissolved at the corresponding invivo time(which can be
calculated easily from any dissolution fitted function which already
i have done in invitro tab)

(2) Fabs = AbsScale * Diss(Tscale * Tvivo)

means :- regression between Fabs (amount absorbed at time vivo for given formulations) vs Diss (Tvivo*Tscale) (amount dissolved at the (corresponding invivo time*Tscale) for given formulations)
here what is the need of intial value or bound to be given for Tscale which can be measured from Tvitro vs Tvivo Levy plot.

y=mx

y= Fabs(amount absorbed at time invivo)
m= Absscale parameter

x=amount dissolved at the (at time invivo*Tscale)
this amount(X) can be calulated from any dissolution data fitted model eg. hill, weibull which already i have done in invitro tab if i have Tscale
parameter obtained from Tvitro vs Tvivo Levy plot

Also when performing regression (most probably linear or is it NONLINEAR if it is in nonlinear regression i think Absscale parameter's initial value or bound should be provided) between Fabs(amount absorbed at time invivo) vs amount dissolved at the (at time invivo*Tscale) Absscale parameter which can be calculated by simple regression-analysis equation THAN WHY BOUNDS OR INITIAL VALUE
SHOULD BE GIVEN
y=mx

y= Fabs(amount absorbed at time invivo)
x=amount dissolved at the (at time invivo*Tscale)
m= Absscale parameter


Please correct me if i am wrong..i will highly appreciate your response

Vijay