Fluoroquinolone medicines (ciprofloxacin, delafloxacin, levofloxacin, moxifloxacin, and

ofloxacin)

Mechanism of action

• inhibit topoisomerase II (DNA gyrase) and topoisomerase IV

Mechanism of resistance

• mutations to DNA gyrase, efflux pumps which reduce intracellular quinolone concentration

Adverse effects

• lower seizure threshold in patients with epilepsy
• tendon damage (including rupture) - the risk is increased in patients also taking steroids
• cartilage damage has been demonstrated in animal models and for this reason quinolones are generally avoided (but not necessarily contraindicated) in children
• lengthens QT interval
• increased risk of heart valve regurgitation
• small increased risk of aortic aneurysm and dissection
• suicidal thoughts

Contraindications

• Quinolones should generally be avoided in women who are pregnant or breastfeeding
• avoid in G6PD

Enzyme Inducers and Inhibitors

In 2024, the Medicines and Healthcare products Regulatory Agency (MHRA) stated that fluoroquinolones should only be used when first-line antibiotics are unsuitable due to resistance, contraindications, intolerance, or failure. MHRA warns of rare but potentially long-term or irreversible side effects affecting the musculoskeletal, nervous, psychiatric and sensory system