High performance liquid chromatographic determination of ciprofloxacin in human plasma and urine and its application to pharmacokinetic studies

A simple, highly sensitive and selective reversed-phase HPLC assay with UV detection for the determination of ciprofloxacin in human plasma and urine was developed and validated. The drug and internal standard, ofloxacin, were extracted from plasma or urine with isopropanol:methylene chloride (1:9, v/v) and back extracted with orthophosphoric acid. Separation was achieved on a C18 reversed-phase column with a mobile phase of acetonitrile:methanol:0.1M sodium dihydrogen orthophosphate:triethylamine:glacial acetic acid (8:10:83:1:2, v/v) and UV detection at 278 nm. The chromatograms were free from interference at the retention times of ciprofloxacin and the internal standard while both compounds eluted as completely resolved peaks. The calibration curves were linear (r2 %ge; 0.996) over concentration ranges of 0.01 to 3.0 µg/ml in plasma and 0.05 to 5.0 µg/ml in urine. The method was reproducible with coefficients of variation 98% in both plasma and urine. The method was successfully applied to estimate the pharmacokinetics of ciprofloxacin after oral administration of a 500 mg dose of ciprofloxacin tablets to 12 healthy volunteers. Key words: Ciprofloxacin; Reversed-phase HPLC; Pharmacokinetics; Ofloxacin Journal of Pharmacy and Bioresources Vol. 2 (1) 2005: 55-6