Study group discussion: Why does ciprofloxacin cause tendinitis or tendon rupture?
The exact pathophysiology of FQ-induced tendinopathy remains elusive; however, some concepts have been suggested:
1. FQs are synthetic antibiotics that act by inhibiting bacterial DNA gyrase (topoisomerase II). DNA gyrase is directly involved in DNA replication and cell should not exert a negative effect on human cell lines because the affected bacterial enzymes have little homology with mammalian DNA gyrase. However, it is possible that FQs have a direct cytotoxic effect on enzymes found in mammalian musculoskeletal tissue.
2. FQs have chelating properties against several metal ions (e.g., calcium, magnesium, aluminum), and have been known to cause direct toxicity to type 1 collagen synthesis and promote collagen degradation.
3. Animal studies have shown that FQs cause cartilage damage by inducing necrosis of chondrocytes (36 hours after treatment), disruption of the extracellular matrix, and formation of vesicles and fissures at the articular surface.