## CVwithin calculation of biperiden [Power / Sample Size]

Hello,
I am trying to find the CVwithin of biperiden immediate release but I am struggling to find any literature on bioequivalence of biperiden. However, I found a cross-over study comparing pharmacokinetics of biperiden immediate release against extended release.
Is it reasonable to assume the CVwithin of biperiden to be equal to the one on the study that I found? I mean, I think it will be smaller or equal at most, therefore if I assume it is the same for the sake of sample size calculation, I could be overestimating sample size, but I would not be sacrificing any statistical power, which is not statistically incorrect, right?

Any help is welcome.
many thanks