Microstructures are a critical characteristic to generic drug bioequivalence, as designated in the FDA's Q3 component of product similarity. In this study, a brand name controlled release ibuprofen drug was found to have a steady release of the applied pharmaceutical ingredient (API), while the generic drug had an irregular release. We used a FIB-SEM imaging technique to slice open and visualize the cross section of the drug pellets. Images revealed uniform porous networks in the brand name drug and microfracture structures in the generic drug, in part accounting for their different performance. This analysis determined that the generic product was far from achieving microstructure bioequivalence. Beyond imaging, our analysis can be applied to quantify critical parameters such as drug particle size distribution, spatial homogeneity, microporosity, and amorphous phases.