Validation of a reversed-phase LC method for quantitative analysis of intravenous admixtures of ciprofloxacin and metronidazole.

The admixture ciprofloxacin-metronidazole is nowadays well known as a clinical tool when anaerobic organisms are involved. The stability of ciprofloxacin with metronidazole depends on several variables and this has been scarcely studied. Thus, the aim of this study was the search for a specific, precise and accurate method that would allow the quantification of ciprofloxacin in the presence of metronidazole. The reversed-phase liquid chromatography method is the analytical technique that has proved to be the most adequate for stability and compatibility studies of this mixture. This method was shown to be linear (r>0.999) in the range of concentrations of this study chosen, between 80 and 120% of the concentration of the commercial formulation. It showed precision with a repeatability (within-day) of 0.62% and reproducibility (between-day) of 1.14%, accuracy expressed as recovery percentage.