Bioequivalence and Bioavailability Forum

Hi sury,

❝ Can anyone have any idea how can we provide sample size for the PD endpopints

The overarching principle is the same:
You need to guesstimate the resemblance along with the variability of the quantity on which equivalence is determined. The first one is entirely formulation dependent, the latter is biological in nature.
In consequence you first decide on the design and the stats model, and then you work out the sample size from that model.

You will need to be very, very specific in order for anyone here to help you with the actual sample size. Very often you will not find info in the public domain that can be used to calculate sample size (like variability for certain nasal and inhalation drug PD endpoints). In those cases where you can't look up variability in literature/FOI act access/journals/etc you will not get a qualified sample size without at least a pilot study.
Note also that for FDA some PD endpoints are complex in that superiority to placebo is required along with proof of equivalence for T vs R. This is not always entirely straightforward.