Topical Fluocinonide and Tachyphylaxis

To the Editor.—  The May 1982 Archives (118:305-308) contained a thought-provoking study by Du Vivier et al, which showed that application of a 0.05% fluocinonide ointment once or twice daily caused notable inhibition of DNA synthesis in hairless mouse skin for approximately 100 hours. However, continued use of the two regimens then resulted in increased levels of DNA synthesis.This finding is consistent with previously published reports that tachyphylaxis to repeated daily application of corticosteroids, which included fluocinonide cream, occurs in both normal human skin (as determined by diminishing vasoconstriction with continued applications¹) and in hairless mouse skin (in which mitosis was noted to be increased with repeated treatments after being decreased initially²).Since topical adrenal corticosteroids may exert their therapeutic activity in psoriasis by inhibiting epidermal DNA synthesis and mitosis,³ the experimental findings that tachyphylaxis to repeated daily topical corticoid treatments develops in both man and