title: Photodegradation of moxifloxacin in aqueous and organic solvents: a kinetic study.
abstract: The kinetics of photodegradation of moxifloxacin (MF) in aqueous solution (pH 2.0-12.0), and organic solvents has been studied. MF photodegradation is a specific acid-base catalyzed reaction and follows first-order kinetics. The apparent first-order rate constants (kobs) for the photodegradation of MF range from 0.69 × 10(-4) (pH 7.5) to 19.50 × 10(-4) min(-1) (pH 12.0), and in organic solvents from 1.24 × 10(-4) (1-butanol) to 2.04 × 10(-4) min(-1) (acetonitrile). The second-order rate constant (k2) for the [H(+)]-catalyzed and [OH(-)]-catalyzed reactions are 6.61 × 10(-2) and 19.20 × 10(-2) M(-1) min(-1), respectively. This indicates that the specific base-catalyzed reaction is about three-fold faster than that of the specific acid-catalyzed reaction probably as a result of the rapid cleavage of diazabicyclononane side chain in the molecule. The kobs-pH profile for the degradation reactions is a V-shaped curve indicating specific acid-base catalysis. The minimum rate of photodegradation at pH 7-8 is due to the presence of zwitterionic species. There is a linear relation between kobs and the dielectric constant and an inverse relation between kobs and the viscosity of the solvent. Some photodegraded products of MF have been identified and pathways proposed for their formation in acid and alkaline solutions.
authors.affiliation: Baqai Institute of Pharmaceutical Sciences, Baqai Medical University, Toll Plaza, Super highway, Gadap Road, Karachi, 74600, Pakistan.
authors.forename: Iqbal
authors.initials: I
authors.lastname: Ahmad
authors.forename: Raheela
authors.initials: R
authors.lastname: Bano
authors.forename: Syed Ghulam
authors.initials: SG
authors.lastname: Musharraf
authors.forename: Sofia
authors.initials: S
authors.lastname: Ahmed
authors.forename: Muhammad Ali
authors.initials: MA
authors.lastname: Sheraz
authors.forename: Qamar
authors.initials: Q
authors.lastname: ul Arfeen
authors.forename: Muhammad Salman
authors.initials: MS
authors.lastname: Bhatti
authors.forename: Zufi
authors.initials: Z
authors.lastname: Shad
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000528:radiation effects*; D002626:Chemistry, Pharmaceutical; D002851:Chromatography, High Pressure Liquid; D004355:Drug Stability; D024841:Fluoroquinolones / Q000737:chemistry / Q000528:radiation effects*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008027:Light; D016014:Linear Models; D008956:Models, Chemical; D000077266:Moxifloxacin; D009930:Organic Chemicals / Q000737:chemistry*; D010782:Photolysis; D015203:Reproducibility of Results; D012997:Solvents / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry; D013678:Technology, Pharmaceutical / Q000379:methods; D014783:Viscosity
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D009930:Organic Chemicals; D012997:Solvents; D000077266:Moxifloxacin