Fluoroquinolone Antibiotic Pregnancy: Avoid — theoretical cartilage risk based on animal data

Ciprofloxacin (Orthopaedic — Gram-negative Osteomyelitis)

Brand names: Ciproxin

Adult dose

Dose: 500–750 mg twice daily (oral); 400 mg IV every 8–12 hours (IV)

Route: Oral or Intravenous

Frequency: Twice daily (oral); every 8–12 hours (IV)

Max: 1500 mg/day oral; 1200 mg/day IV

Excellent oral bioavailability (~80%) — IV only where oral not possible. Best fluoroquinolone bone penetration (2–6× serum levels in bone). Used for Gram-negative osteomyelitis (Pseudomonas, Enterobacteriaceae). MHRA 2019 and 2023: serious tendon, nerve, and CNS side effects — prescribe only when clearly necessary and after benefit-risk assessment.

Paediatric dose

Dose: 10–20 mg/kg

Route: Oral or IV

Frequency: Twice daily

Max: 750 mg per dose

Paediatric use — generally avoided due to arthropathy concerns in weight-bearing joints in animal models; use only when benefit clearly outweighs risk (cystic fibrosis, Pseudomonas osteomyelitis)

Dose adjustments

Renal

eGFR 30–60 mL/min: reduce dose to 250–500 mg BD; eGFR <30 mL/min: 250–500 mg once daily

Hepatic

Use with caution in severe hepatic impairment

Paediatric weight-based calculator

Patient weight (kg)

Paediatric use — generally avoided due to arthropathy concerns in weight-bearing joints in animal models; use only when benefit clearly outweighs risk (cystic fibrosis, Pseudomonas osteomyelitis)

Clinical pearls

MHRA 2019: Disabling and potentially irreversible side effects — tendonitis, tendon rupture, peripheral neuropathy, CNS effects; use only when clearly necessary; stop immediately if any of these develop
MHRA 2023: Updated guidance reinforces restricted use — fluoroquinolones should NOT be first-line for most infections; reserve for Gram-negative osteomyelitis (including Pseudomonas) where no suitable alternative exists
Best bone penetration of all oral antibiotics: ciprofloxacin achieves 2–6× serum levels in cortical and cancellous bone — the only oral antibiotic with reliable Pseudomonas coverage and good bone penetration
Chelation absorption interaction: antacids (especially aluminium/magnesium), calcium supplements, iron tablets, and dairy products can reduce ciprofloxacin oral absorption by up to 90% — take ciprofloxacin on empty stomach, ≥2 hours before or 6 hours after these agents
Paediatric arthropathy: ciprofloxacin causes cartilage erosions in weight-bearing joints of immature animals — historically avoided in children; however, clinical evidence of arthropathy in children is limited; used when benefit outweighs risk (Pseudomonas, CF)

Contraindications

History of fluoroquinolone-induced tendon disorders
Concurrent QT-prolonging drugs (additive QTc risk)
Myasthenia gravis (fluoroquinolones worsen neuromuscular block)

Side effects

Tendonitis and tendon rupture — Achilles tendon most common; MHRA 2019 warning
Peripheral neuropathy — may be irreversible
CNS effects — seizures, confusion, psychiatric symptoms
QTc prolongation
GI effects — nausea, diarrhoea
C. difficile infection
Photosensitivity

Interactions

Antacids, calcium, iron, magnesium — chelate ciprofloxacin; reduce absorption by 50–90%; separate by 2 hours
Warfarin — increases INR significantly via CYP1A2 inhibition; monitor INR closely
Theophylline — reduces theophylline clearance; toxicity risk; reduce theophylline dose
NSAIDs — additive seizure risk

Monitoring

Tendon pain or swelling — especially Achilles
Peripheral neurological symptoms
QTc if on QT-prolonging drugs
LFTs and renal function
INR if on warfarin

Reference: BNFc; BNF 90; MHRA DSU 2019 and 2023 (Fluoroquinolone Restrictions); IDSA Osteomyelitis Guidelines 2012; NICE Antimicrobials; SPC Ciproxin. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

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