POSTDOCTORAL FELLOW Rutgers, the State University of New Jersey Piscataway, New Jersey, United States
Background: Topical corticosteroids (TCs) are highly effective in the treatment of inflammatory skin conditions such as eczema and psoriasis, when prescribed and used appropriately. TC products are available in different potencies which depend on the specific therapeutic indication. The potency of TCs is important because the clinical choice of a TC depends on various factors which are considered by dermatologists when prescribing such products to achieve optimum safety and efficacy. In May 2024, the Medicines and Healthcare Products Regulatory Agency (MHRA), UK, announced that TC products must be labelled with their potencies to aid correct selection and to simplify the advice to patients requiring multiple steroid products of differing potencies1. Potencies of TC products have usually been classified based on clinical or vasoconstrictor assay (VCA) data. However, several discrepancies exist in various published potency classifications leading to ambiguity. Therefore, we propose the classification of TC active pharmaceutical ingredients (APIs) based on their inherent potencies using the Food and Drug Administration’s (FDA’s) VCA. Methods: Standardized solutions (0.0025M) of TCs in a common vehicle were prepared and applied to the forearms of healthy human participants. The skin blanching response produced by the TCs was measured using a chromameter. The resultant VCA data was fitted using the Emax model, and the pharmacodynamic parameters, Emax and ED50, were derived. Since Emax has shown to correlate with potency, it was used as a metric to assess the potencies and rank the TCs. Results: The blanching response profiles (Figure 1) showed a direct correlation between the dose duration and skin blanching response, where an increase in dose duration resulted in an increase in the skin blanching response. Mometasone furoate demonstrated the highest Emax value (-55.27 ± 8.19) followed by hydrocortisone butyrate (-48.82 ± 21.90), and methylprednisolone aceponate had the lowest Emax value (-37.49 ± 14.79). Hence, the inherent potency of mometasone furoate > hydrocortisone butyrate > methylprednisolone aceponate. Conclusion: Inherent potency assessment of TCs provides useful information when choosing an appropriate TC for a specific clinical indication. The FDA’s VCA is an optimal method to assess the potency of TC APIs and formulated TC products.
