[Concentration of ciprofloxacin in bone tissue]

After the administration of a 200 mg i.v. dose, the concentration of ciprofloxacin in bone and serum of 20 patients with coxarthrosis was determined before implantation of a total hip-joint endoprosthesis. Samples were taken from the cortical bone and cancellous bone either 1 hour, 2 hours, 3 hours, 4 to 5 hours, or 13 to 19 hours after administration. Blood samples for the determination of serum concentration were also taken at these times. The bone samples were extracted three times in phosphoric acid (10 mmol/l) at 4 degrees C for 20 hours, the volume of phosphoric acid being ten times that of the bone sample. The ciprofloxacin concentration was determined by high-performance liquid chromatography and fluorescence detection. The bone concentration was referred to bone volume by assuming a bone density of 1.9 g/l. The mean bone concentrations in cancellous and cortical bone after ciprofloxacin administration were, respectively, 2.16 mg/l and 1.42 mg/l after 1 hour; 0.82 mg/l and 0.56 mg/l after 2 hours; 2.50 mg/l and 1.04 mg/l after 3 hours; 1.16 mg/l and 0.42 mg/1 after 4-5 hours; and 0.27 mg/l and 0.15 mg/l after 13-19 hours. Ciprofloxacin quickly penetrated the bone. The ratio of areas under the curve (AUC) from bone to serum was 2.24 for cancellous and 0.99 for cortical bone. In 16 out of 19 bone samples, the ciprofloxacin concentration measured was higher than the MIC90 for Staphylococcus aureus.