Penetration of Ciprofloxacin into Bone: A New Bioabsorbable Implant

Abstract

The implantation of antibiotic-containing cement beads became standard adjuvant local antibiotic therapy of chronic osteomyelitis. The new developed bioabsorbable drug carrier system of polyglycolic acid with the antibiotic Ciprofloxacin was tested in vitro and in vivo. The goal of this study was to determinate the penetration depth of Ciprofloxacin into bone cortex and marrow. Two monofil, PGA cylinders, 3.2 × 5 mm in size, containing 3 mg of Ciprofloxacin each, were implanted into the proximal part of both femora of 18 rabbits (New Zealand white). After sacrifice, the concentration of Ciprofloxacin in μg/g cortex and marrow was measured with high-performance liquid chromatography in relation to the distance from the test material at day 2, as well as at 1, 2, 3, 4, and 6 weeks postimplantation. For a distance up to 5 mm, marrow levels of the drug exceeded cortical levels at day 2 (5000 to 240 μg/g). At a distance of 5–10 mm, cortex levels were similar to marrow levels after 2 weeks and were higher than marrow levels at week 3. This observation could be made at a distance between 10 and 15 mm only after 2 days. Later, marrow concentrations again exceeded that in cortex. At a distance of more than 15 mm, antibiotic levels were low and approximated. After 6 weeks, at 5 mm distance, a bactericidal drug concentration of about 2 μg/g in bone marrow could be measured. Drug penetration into cortical bone in bactericidal concentrations of about 2 μg/g was achieved at up to 30 mm in the first few days. After 4 weeks of implantation, bactericidal levels were measured up to a penetration depth of nearly 10 mm. The study showed a significantly greater penetration of Ciprofloxacin into bone than has been reported for Gentamycin cement beads.

Key Words:

• Ciprofloxacin
• polyglycolic acid carrier
• osteomyelitis
• drug penetration into bone
• local antibiotic therapy
• drug delivery system