Bioequivalence and Bioavailability Forum

This is how I will plan for retention samples. Maximum quantity of retention samples is 300 units (tablets or injections etc.).

1. procure 300 units per manufacturing batch (for this reason better to keep to one lot)
   
2. distribute portion of these 300 retentions samples to each center along with each shipment (again you are better off with one shipment though you have not much control)
   
3. you ship required clinical IDP to each center and ask them to aliquot and keep the representative retention samples for test and reference products at each site. at the end of the study all clinical sites are expected to ship the retention samples for storage to the reminder of the required duration. Usually this would be at a CRO site equipped to store retention samples.
   
   
4. Recently FDA published a guidance on retention samples, which gives a provision to request the FDA seeking waiver for keeping lesser quantity of retention samples (you better initiate such correspondence before the study start to avoid any surprises

“For products not included in Appendix 1, NDA and ANDA applicants or CROs should submit requests that FDA not take action if they wish to retain less than the quantity of reserve samples of the test product and reference standard used in BA or BE testing set forth in 21 CFR 320.38(c).”

Hope this helps.