Abstract B9
HPLC/UV And HPLC/MS Detection of Clobetasol Propionate as an Undeclared Steroid in Zinc Pyrithione Formulations
John C. Reepmeyer¹, Larry K. Revelle¹, and Ilan Vidavsky². ¹Division of Testing and Applied Analytical Development, FDA, St. Louis, MO; ²Washington University Mass Spectrometry Resource, Washington University, St. Louis, MO.

Clobetasol propionate, an anti-inflammatory glucocorticosteroid, was detected in an over-the-counter topical drug product with no indication on the label of this compound as an ingredient. The pharmaceutical product, labeled to contain zinc pyrithione as its active ingredient, was formulated as a topical spray, a cream, and a shampoo. The presence of clobetasol propionate in these products was shown by comparison to a clobetasol propionate standard by retention time on normal phase and reversed phase HPLC, UV spectroscopy, LC/MS, and LC/MS/MS. Eight lots (4 sprays, 2 creams, and 2 shampoos) contained clobetasol propionate at therapeutic levels of 0.02-0.06%, one lot (spray) contained only a trace amount, and one lot (shampoo) contained none.