The Vasoconstrictor Assay ( VCA ): Then and Now

Application of Emax model to assess the potency of topical corticosteroid products

“…Blinding of the operator/ data analyst was deemed unnecessary because the final results are independent of operator/data analyst bias. Only the a ‐scale data were used in the statistical analysis in accordance with the FDA guidance 24,26–28 . In accordance with the policies at the Biopharmaceutics Research Institute (BRI), all study data (source documents, study reports and other study documentation) obtained at the institute are archived and retained for a period of 10 years.…”

“… where E is the pharmacodynamic effect metric, that is, AUEC ; D is the duration of exposure (min) to the TC; E max is the maximum possible value for E ; ED 50 is the dose duration necessary to achieve 50% of the E max response. Although the FDA's VCA guidance recommends the use naive pooling or non‐linear mixed effect modelling (NLME) to fit the pharmacodynamic response data, 20,26,29,30 naive pooling does not take into consideration the inter‐individual variability, which may not accurately represent the study population 29,30 . Therefore, P‐Pharm software, which uses NLME modelling with the likelihood estimation, 30,31 is a more appropriate method for the determination of population parameters such as ED 50 and E max 30 …”