A simple and sensitive high-performance liquid chromatography method for determination of ciprofloxacin in bioavailability studies of conventional and gastroretentive prolonged-release formulations

Background: A very simple, sensitive, and accurate high-performance liquid chromatography (HPLC) method with ultraviolet detector was developed and applied to determine ciprofloxacin in human plasma following administration of a gastroretentive formulation developed in our laboratory.
Materials and Methods: HPLC analysis was performed on a C₁₈μ-Bondapack column (250 mm × 3.9 mm) using acetonitrile: potassium dihydrogen phosphate solution 0.1 M (20:80, v/v, pH 3) at a flow rate of 1.5 ml/min and eluate was monitored at 276 nm. After addition of phenacetin as internal standard, plasma samples were treated with 0.1 M phosphate buffer (pH: 7) and followed by extraction with dichloromethane. The method was validated for linearity, precision, accuracy, limit of quantitation (LOQ), robustness, stability, and applied in bioavailability studies of our developed gastroretentive formulation in healthy volunteers.
Results: The calibration curves were linear over the concentration range 0.025–4 μg/ml with the detection limit of 15 ng/ml. Accuracy % were within 93–115 and the coefficient of variance % ranged from 0.20 to 12.8. The very low LOQ (25 ng/ml) allowed avoiding fluorometric detection which is more expensive and is not available in all laboratories. Ciprofloxacin was stable in samples with no evidence of degradation during 3 freeze-thaw cycles and 3 months storage at –70°C.
Conclusion: This validated HPLC method was successfully used for the determination of ciprofloxacin in human plasma following oral administration of controlled release formulation, conventional immediate-release tablets and when administered concomitantly with divalent and trivalent cations such as aluminum-, magnesium-, or calcium-containing products under which the bioavailability of ciprofloxacin is significantly reduced.