title: Effect of titanium dioxide on photostability of solid-state mequitazine.
abstract: TiO(2) has been widely used in pharmaceutical products, and it also has been used as a photocatalyst. In this study, the influence of photocatalytic activity on the stability of solid-state mequitazine, an H(1)-blocker, was investigated. The photo-degradation of mequitazine with TiO(2) occurred under irradiation with both light sources. The degree of degradation of mequitazine with anatase was higher than that of rutile. The degradation was significantly enhanced with increasing relative humidity. The relationship between the apparent degradation rate constant and water vapor pressure could be clearly described by a simple power law. The major photo-degradation products of mequitazine, resulting from photocatalytic activity of TiO(2), were mequitazine-S-oxide and mequitazine-sulphone. A remarkable degradation of mequitadine occurred with addition of TiO(2), and its photocatalytic activity was controlled by water vapor pressure. The photo-degradation of mequitazine with TiO(2) is a different process from mequitazine without TiO(2), because mequitazine-S-oxide and mequitazine-sulphone are not formed with normal photo-degradation of mequitazine.
authors.affiliation: Formulation & Industrial Technology Lab., Taiho Pharmaceutical Co., Ltd.; Tokushima 771-0194, Japan. k-kakinoki@taiho.co.jp
authors.forename: Koichi
authors.initials: K
authors.lastname: Kakinoki
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamane
authors.forename: Manami
authors.initials: M
authors.lastname: Yamamoto
authors.forename: Reiko
authors.initials: R
authors.lastname: Teraoka
authors.forename: Isao
authors.initials: I
authors.lastname: Sugimoto
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Matsuda
mesh_terms: D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D003116:Color; D004355:Drug Stability; D006634:Histamine H1 Antagonists / Q000737:chemistry* / Q000528:radiation effects; D006813:Humidity; D008027:Light; D013058:Mass Spectrometry; D010640:Phenothiazines / Q000737:chemistry* / Q000528:radiation effects; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D014025:Titanium / Q000737:chemistry*
chemical_list: D006634:Histamine H1 Antagonists; D010640:Phenothiazines; D017319:Photosensitizing Agents; C009495:titanium dioxide; D014025:Titanium; C006069:mequitazine