Influence of Cosolvents and Surfactants on the Rate Constant (Log K) of Sparfloxacin

Sparfloxacin, a difluoroquinolone antibacterial agent is clinically used in the treatment of streptococci and community-acquired lower respiratory tract infections. The aim of the present study was to investigate to what extent cosolvents and surfactants could affect sparfloxacin degradation kinetics under acidic condition. The degradation of sparfloxacin in acidic aqueous solution of cosolvents and surfactants at 60 ± 0.2°C was studied. The degradation was determined by UV spectrometry. The degradation was observed to follow apparent first-order rate kinetics and the rate constants for the decomposition were obtained from plots of logarithm percent drug concentration remaining versus time. The reaction was shown to be hydrogen ion catalysed. Significant increase in the stability of sparfloxacin was observed with the cosolvents and surfactants investigated. The study suggests that cosolvents or surfactants at non-toxic concentrations could be incorporated into liquid pharmaceutical dosage forms of sparfloxacin to stabilize the preparations under acidic conditions.