Generic dry powder inhalers bioequivalence: Batch–to-batch variability insights

•Batch-to-batch bioinequivalence has negligible clinical downsides.•Choice of Reference batch for generic bioequivalence testing is significant.•To date, different regulations do not address the batch-to-batch variability issue.•Respiratory specific and reliable in vitro dissolution tests and IVIVC are needed.•Inherent factors in DPI formulations contribute to the batch-to-batch variability.