Determination of Ciprofloxacin in Dried Blood Spots for Therapeutic Drug Monitoring

The use of blood spot collection cards is a simple way to obtain specimens for analysis of drugs for the purpose of therapeutic drug monitoring, assessing adherence to medications and preventing toxicity in certain groups of patients. We describe the development and validation of a microanalytical technique for the determination of ciprofloxacin from dried blood spots. The method is based on reversed phase liquid chromatography with fluorescence detection. Drug recovery in the developed method was found to be higher than 95%. The limits of detection and quantification were calculated to be to be 60 and 100 ng mL⁻¹, respectively. The intra- and inter-day precision (measured by CV%) was always less than 6% (13.07% at LOQ). The accuracy (measured by relative error, %) was always less than 8% (7.82% at LOQ). Stability analysis showed that ciprofloxacin is stable for at least 1 month when stored at −70 °C. The small volume of blood required (30 μL), combined with the simplicity of the analytical technique makes this method a potential procedure for monitoring ciprofloxacin concentrations in certain patient populations.