Bioequivalence and Bioavailability Forum

Can someone throw light on how to compute number of retention samples needed for a multi center patient trial. Is it N=30/center/shipment (some centers may recruit one or 2 patients) or N=30/batch/shipment to CRO and CRO will uniformly distribute across different centers based on the recruitment rate.

We have to be mindful some RLDs are cost prohibitive e.g. 1 pre-filled syringe can be $ 8000