Photodegradation of levofloxacin in aqueous and organic solvents: A kinetic study

Abstract

The kinetics of photodegradation of levofloxacin in solution on UV irradiation in the pH range 2.0-12.0 has been studied using a HPLC method. Levofloxacin undergoes first-order kinetics in the initial stages of the reaction and the apparent first-order rate constants are of the order of 0.167 to 1.807×10-3 min-1. The rate-pH profile is represented by a curve indicating the presence of cationic, dipolar and anionic species during the reaction. The singly ionized form of the molecule is non-fluorescent and is less susceptible to photodegradation. The increase in the degradation rate in the pH range 5.0-9.0 may be due to greater reactivity of the ionized species existing in that range. The rate appears to vary with a change in the degree of ionization of the species present in a particular pH range and their susceptibility to photodegradation. Above pH 9, the decrease in the rate of photodegradation may be a result of deprotonation of the piperazinyl group. The levofloxacin molecule is more stable in the pH range around 7, which is then suitable for formulation purposes. The photodegradation of levofloxacin was found to be affected by the dielectric constant and viscosity of the medium

Photo, thermal and chemical degradation of riboflavin

“…The dependence of flavin triplet state quenching on solvent viscosity has previously been reported [50]. A similar linear relationship between the rate constants and inverse of solvent viscosity has also been reported for ascorbic acid [104] and levofloxacin [105]. …”

Solvent Effect on the Photolysis of Riboflavin

“…The viscosity of the medium may also affect the stability of a drug. A linear relation has also been found between the rate constant and the inverse of solvent viscosity for the photodegradation of 10-methylisoalloxazine (12), formylmethylflavin (9), levofloxacin (6), and moxifloxacin (4) in organic solvents.…”

“…Theoretical basis of the effects of solvent on the rates and mechanism of chemical reactions has been extensively dealt by many workers (14,18,21,28,37,47,56,65). The effect of dielectric constant on the degradation kinetics and stabilization of chloramphenicol (40), barbiturates (31), methanamine (59), ampicillin (29), prostaglandin E 2 (48), chlorambucil (43), 2-tetrahydropyranyl benzoate (30), indomethacin (24), aspirin (16), phenoxybenzamine (2), azathioprine (55), polypeptides (17), neostigmine (64), triprolidine (39), 10-methylisoalloxazine (12), formylmethylflavin (7), levofloxacin (6), and moxifloxacin (4) has been reported. The viscosity of the medium may also affect the stability of a drug.…”

Aqueous Ultrasound-Assisted Extraction for the Determination of Fluoroquinolones in Mangrove Sediment by High-Performance Liquid Chromatography and Fluorescence Detector

“…In Table 1 are described the physicochemical properties and chemical structure of some fluoroquinolones: ciprofloxacin (CIP), levofloxacin (LEV) and norfloxacin (NOR). 13,17 CIP, LEV and NOR have been used in human medicine. CIP and NOR are also used in veterinary applications.…”