Abstract
Various potency classification listings for topical corticosteroid
products (TCPs) have been based on clinical data and/or data using the
US FDA’s vasoconstrictor assay (VCA). However, studies that used VCA
data mainly used a single visual measurement and often the doses and
dose durations were not determined in accordance with the VCA
requirements. The objective was to compare the potencies of two TCPs
using the Emax model to fit the blanching responses obtained from the
VCA as described in a previous publication and to illustrate the
influence of formulation on potency. The potencies of two marketed
creams, Dermovate® containing clobetasol propionate (CP) and Elocon®
containing mometasone furoate (MF) were assessed using healthy human
subjects. In order to investigate the influence of formulation and
associated vehicle properties, the TCPs were compared to their
respective TCs from a previously published study wherein the inherent
potencies of those TCs were assessed using a validated VCA method.
Whereas the inherent potency of MF (Emax = -94.45 ± 0.21) was found to
be greater than CP (Emax = -58.80 ± 15.65), when formulated as creams,
the TCP containing CP had a higher potency (Emax = -86.15 ± 0.17) than
that containing MF (Emax = -42.61 ± 26.04). This reversal of potency may
be attributed to the effect of formulation factors. The comparison of
the potencies of TCPs with inherent potencies of their corresponding TCs
confirmed the influence of formulation parameters on the potency of
those products.