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.