Bioequivalence and Bioavailability Forum

Dear yuvrajkatkar,

❝ The maximum Ratio[%Ref]= 90.20% and corresponding Intrasubject CV= 16.04% for Ln(Cmax).

Is the minimum ratio but maximum CV.

❝ If we take T/R ratio = 90.20% and Intrasubject CV= 16.04% then sample size will be greater than 20000 to get 90% confidence intervals of log-transformed Cmax ...

Exactly 63750 (power=80.0003%) using my super code. Approximate Googol !
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❝ Instead of ln(1.25)=0.20, I have taken ln(1.11)=0.10.

ln(1.25) = 0.2231436, ln(1.11)=0.1043600 on my machine (Intel® Pentium 4, 1 GB RAM; Win XP Professional, SAS9.2 or R10.0).
BE upper acceptance limits with your numbers: exp(0.2)=122.14% and exp(0.1)=110.52%.

In the light of the FDA guidance and the new EMA guidance both asking for CI within 80.00 to 125.00 % it is IMHO not a good idea to use only 1 decimal.

❝ Is it right way to choose sample size for the next study

Since I guess your results came from a BE study with approx. 38 subjects why do you expect that your point estimates are unreliable?
With such a point estimate you never achieve BE within the acceptance range 90 ... 111.11%
So the right suggestion for a next study is: reformulate is the question.