Bioequivalence and Bioavailability Forum

Dear Mamidi!

❝ can anybody suggest me the formula or method to calculate a sample size for three period three treatment cross over design by using SAS software. Also please tell me how to get intrasubject variability for a three way cross over design.

I'm not using SAS, but the calculation is not different form a 2×2 design... (for detail have a look at Chow & Liu, 2000, pp 303)

❝ So please give me suggestion or any reference / formula, how to proceed in SAS / WinNonlin software under this situation.

Concerning WinNonlin, I just checked that versions 5.0.1 and 5.1.1 do not give the intra-subject CV for a 3×6 Williams' design (as it does for a 2×2 design in the ASCII output just below the residual-variance line).
Therefore you have to go back to the pre-5.0 method, namely calculating the CV manually!

CV = sqrt(exp(MSE) - 1), where
MSE is the residual variance

You also may use this formula for your SAS-output…

WinNonlin procedure:
In the workbook derived from the BE Wizard
File > Dependencies... > click your workbook > Detach > Yes > Exit
In the workbook navigate to 'Final Variance Parameters' sheet
In the row with parameter 'Var(Residual)' move to the cell right to the 'Estimate' column (generally cell E2), enter
=SQRT(EXP(D2)-1)

Maybe this paper helps?