Bioequivalence and Bioavailability Forum

hi to all,
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.

(Note: We have already done a three way cross-over pilot study under fed conditions for a particular molecule where we did not get intra subject variability and we want to know how much sample size is required for a Pivotal study for the same molecule.)

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

Thanks and Regards,
MGR