title: Photochemistry and phototoxicity of fluocinolone 16,17-acetonide.
abstract: Fluocinolone 16,17-acetonide is a corticosteroid used topically to treat various inflammatory skin diseases. Its photoreactivity was studied under UV-A and UV-B light in aqueous buffer in the presence of oxygen. This drug is photolabile under UV-B light and, to a lesser extent, under UV-A light, which is absorbed far less. In phosphate buffer, approximately 80% of fluocinolone acetonide decomposes after 5 J/cm2 of UV-B irradiation, whereas under 30 J/cm2 of UV-A light approximately only 20% decomposes. Both the drug and its photoproducts have been evaluated through a battery of in vitro studies and found to cause photohemolysis and induce photodamage to proteins (erythrocyte ghosts, bovine serum albumin) and linoleic acid. In addition, one of the photoproducts (the 17-hydroperoxy derivative) is highly toxic in the dark. Therefore, both loss of therapeutic activity and light-induced adverse effects may be expected when patients expose themselves to sunlight after drug administration. A major mechanism for phototoxicity involves radicals forming from drug breakdown, at least under UV-B, although reactive oxygen species may play a role, particularly under UV-A.
authors.affiliation: Department of Pharmaceutical Sciences, University of Padova, Padova, Italy. giorgia.miolo@unipd.it
authors.forename: Giorgia
authors.initials: G
authors.lastname: Miolo
authors.forename: Sergio
authors.initials: S
authors.lastname: Caffieri
authors.forename: Daniele
authors.initials: D
authors.lastname: Dalzoppo
authors.forename: Andrea
authors.initials: A
authors.lastname: Ricci
authors.forename: Elisa
authors.initials: E
authors.lastname: Fasani
authors.forename: Angelo
authors.initials: A
authors.lastname: Albini
mesh_terms: D004307:Dose-Response Relationship, Radiation; D005446:Fluocinolone Acetonide / Q000737:chemistry / Q000494:pharmacology* / Q000528:radiation effects*; D005609:Free Radicals / Q000737:chemistry / Q000528:radiation effects; D019787:Linoleic Acid / Q000737:chemistry / Q000528:radiation effects; D008968:Molecular Conformation; D010100:Oxygen / Q000737:chemistry; D010777:Photochemistry; D013997:Time Factors; D014466:Ultraviolet Rays; D014867:Water / Q000737:chemistry
chemical_list: D005609:Free Radicals; D014867:Water; D005446:Fluocinolone Acetonide; D019787:Linoleic Acid; D010100:Oxygen