(T1330-11-65) Influence of Formulation Factors on Potency of Topical Corticosteroid Creams by Fitting Pharmacodynamic Data to the E_max Model

Purpose: The current topical corticosteroid product (TCP) potency classification lists lack important information viz. formulation type, percentage of TC in the product, and method of classification. Hence, the development of a more consistent classification system using standardised and validated methods is necessary. The main aim of this research was to investigate the effect of formulation factors on the potency of formulated products containing the respective TCs. A further objective was to compare the potencies of two marketed TCPs using a recently published novel approach by Zvidzayi et al.¹ that ranked the inherent potencies of the respective topical corticosteroid (TC) active pharmaceutical ingredients (APIs) using the US Food and Drug Administration’s (FDA’s) vasoconstrictor assay (VCA)².

Methods: The potencies of two cream formulations containing clobetasol propionate (Dermovate^®) and mometasone furoate (Elocon^®) were assessed using ten healthy human participants. The skin blanching data obtained using a chromameter were fitted to an E_max model and the resultant E_max values were compared between the products. In order to investigate the influence of formulation and associated vehicle properties, the E_max data for the TCPs were compared with the corresponding inherent potency data for each API from our previously published study¹.

Results: The mean E_max value for Dermovate^® was significantly greater than that for Elocon^® indicating a higher potency of the former TCP. However, the inherent potency of clobetasol propionate, was lower than that of mometasone furoate. Furthermore, when compared with their respective TCs, Dermovate^® was more potent than its TC whereas Elocon^® cream was less potent than its TC. The pharmacodynamic parameters and the comparisons are depicted in Tables 1 and 2, respectively.

Conclusion: The TCP potency results were in line with existing classification systems. Using the novel potency assessment approach based on E_max data, the potency of TCPs were compared with the inherent potencies of their corresponding TCs which demonstrated the influence of formulation parameters and vehicle components on the potency of those products.

References: 1 Zvidzayi M, Rath S, Bon C, Kanfer I. A Novel Approach to Assess the Potency of Topical Corticosteroids. Pharmaceutics 2021; 13.
2 US Food and Drug Administration. Guidance for Industry: Topical Dermatologic Corticosteroids—In Vivo Bioequivalence; FDA: Silver Spring, MD, USA, 1995.

Acknowledgements:Funding sources: This research was funded by Biopharmaceutics Research Institute, Rhodes University, Grahamstown, South Africa. BRI Grant No. KZ2/19.

Conflicts of interest: None to declare

The assistance by Sr Emily Repinz, the clinical coordinator at the Biopharmaceutics Research
Institute is gratefully acknowledged.


Table 1 Emax and ED50 values obtained for TCPs and their corresponding TCs


Table 2 Pairwise Emax comparisons