Halobetasol versus clobetasol: a study of potency.

Sir, Topical corticosteroids (TCS) are an integral part of dermatological therapeutics. The clinical effects of TCS depend on the structure of the molecule, the vehicle and the skin onto which it is applied.[1] Addition of a fluorine molecule at six and/ or nine positions enhances the potency of TCS. Halobetasol propionate has 6α flouro clobetasol 17-propionate as the active ingredient. Very occlusive vehicles enhance TCS molecule percutaneous absorption probably by increasing the hydration of the stratum corneum.[2] To estimate potency, various assays like vasoconstrictor assay and artificially induced inflammation using ultraviolet light can be used.[1] The ability of TCS to inhibit the size of histamine-induced wheal was used to assess the relative efficacy of halobetasol propionate and clobetasol 17-propionate in cream and ointment formulations in an openlabeled study conducted on 30 volunteers.