Bioequivalence and Bioavailability Forum

Dears

In a BE study of bilayer fixed combination product, one is immediate release and other is sustained, one volunteer in one phase shows no concentrations for the immediate release product (test product) , while the other sustained active ingredient shows normal concentration profile, all other phases in the volunteer also show regular profile for both actives, no evidence for emesis or any adverse event occurred, what is the probability of this case, could this volunteer be outlier, or its related to the formulation and production? what the suggested solution for this case, that could be accepted by authorities?

Thanks