Performance properties of the population bioequivalence approach for in vitro delivered dose for orally inhaled respiratory products.

Regulatory agencies, industry, and academia have acknowledged that in vitro assessments serve a role in establishing bioequivalence for second-entry drug product approvals as well as innovator post-approval drug product changes. For orally inhaled respiratory products (OIPs), the issues of correctly analyzing in vitro data and interpreting the results within the broader context of therapeutic equivalence have garnered significant attention. One of the recommended statistical tests for in vitro data is the population bioequivalence method (PBE). The current literature for assessing the PBE statistical approach for in vitro data assumes a log normal distribution. This paper focuses on an assessment of that assumption for in vitro delivered dose. Concepts in development of a statistical model are presented. The PBE criterion and hypotheses are written for the case when data follows a normal distribution, rather than log normal. Results of a simulation study are reported, characterizing the performance of the PBE approach when data are expected to be normally distributed, rather than log normal. In these cases, decisions using the PBE approach are not consistent for the same absolute mean difference that the test product is from the reference product. A conclusion of inequivalency will occur more often if the test product dose is lower than the reference product for the same deviation from target. These features suggest that more research is needed for statistical equivalency approaches for in vitro data.