What is the recommended dosage of ciprofloxacin (Cipro) for treating bacterial infections?

Ciprofloxacin Dosing for Bacterial Infections

For adults with bacterial infections, ciprofloxacin 500 mg orally every 12 hours or 400 mg IV every 12 hours is the standard dosing regimen, with adjustments based on infection severity and site. 1, 2

Adult Dosing by Indication

Standard Bacterial Infections

• Uncomplicated UTI: 250 mg orally every 12 hours 3
• Complicated UTI: 500 mg orally every 12 hours for 7-20 days (250 mg twice daily shows superior bacteriologic eradication compared to 500 mg once daily) 3
• Severe infections requiring IV therapy: 200 mg IV every 12 hours, with option to transition to 500-750 mg orally every 12 hours after clinical improvement 4, 5
• Nosocomial respiratory tract infections: 200 mg IV every 12 hours (effective for Enterobacteriaceae and H. influenzae; higher doses may be needed for Pseudomonas) 6
• Osteomyelitis/septic arthritis: 300 mg IV every 12 hours initially, followed by oral therapy for mean total duration of 31 days 5

Bioterrorism/Special Pathogens

• Inhalational anthrax (post-exposure prophylaxis): 500 mg orally every 12 hours for 60 days 7, 1
• Cutaneous anthrax (naturally acquired): Penicillin V is preferred; ciprofloxacin 500 mg orally twice daily for 60 days is reserved for bioterrorism-related cases 7
• Necrotizing soft tissue infections (Aeromonas, Vibrio): 500 mg IV every 12 hours in combination with doxycycline or ceftriaxone 7

Pediatric Dosing

Standard Pediatric Regimen

• Weight-based dosing: 10-15 mg/kg orally every 12 hours, maximum 1 g/day regardless of weight 7, 1, 2
• IV dosing: 10 mg/kg IV every 8-12 hours, maximum 400 mg/dose 7
• Children ≥45 kg: May use adult dosing (500-750 mg every 12 hours) 1

Neonatal Dosing

• 15 mg/kg/dose orally every 12 hours (no IV recommendations available for neonates) 7, 2

Special Pediatric Indications

• Multidrug-resistant organisms: 10-20 mg/kg/dose orally every 12 hours (maximum 750 mg/dose); 10 mg/kg/dose IV every 8-12 hours (maximum 400 mg/dose) 7
• Plague treatment: 10 mg/kg IV every 8-12 hours (maximum 400 mg/dose IV) or 15 mg/kg orally every 8-12 hours (maximum 500 mg/dose every 8 hours or 750 mg/dose every 12 hours) 1
• Anthrax post-exposure (children): 10-15 mg/kg orally every 12 hours for 60 days, maximum 1 g/day 1

Critical Pediatric Caveat

Ciprofloxacin should only be used in children for FDA-approved indications (inhalational anthrax, complicated UTI, plague) or when no alternative exists, due to risk of permanent cartilage damage in weight-bearing joints. 2 Pediatric infectious disease consultation is strongly recommended before initiating therapy in children. 7

Pharmacokinetic Considerations

Absorption and Timing

• Oral ciprofloxacin achieves maximum serum concentrations 1-2 hours after dosing with excellent bioavailability 2
• Must be administered at least 2 hours before or 6 hours after products containing divalent cations (calcium, magnesium, iron, aluminum, zinc) to avoid reduced absorption 1

Therapeutic Drug Monitoring

For severe infections with poor clinical response, target serum levels are: 2

• 500 mg twice daily: Trough 1 mg/L, peak 3 mg/L
• 750 mg twice daily: Trough 1.5 mg/L, peak 4.5 mg/L

Special Populations

Pregnancy

• Use only for life-threatening infections where benefits outweigh risks (e.g., inhalational anthrax: 500 mg every 12 hours for 60 days) 1, 2
• Alternative antibiotics (ampicillin, cefotaxime, ceftriaxone) are strongly preferred for routine infections 2

Monitoring Requirements

• ECG monitoring: Baseline, 2 weeks, and after adding any QT-prolonging medication (risk of QTc prolongation) 1, 2
• Blood glucose monitoring: Required in diabetic patients due to hypoglycemia risk 1, 2
• Hepatic and renal function: Monitor intermittently throughout treatment 1, 2

Common Pitfalls

Pseudomonas Infections

Resistance develops rapidly in P. aeruginosa infections, particularly with 200 mg IV every 12 hours dosing. 6 Seven of 10 pneumonia patients and all patients with lung abscess/bronchiectasis developed resistance during therapy. 6 Consider higher doses or combination therapy for Pseudomonas infections, particularly in respiratory tract. 6

Dosing Frequency Errors

Once-daily dosing (500 mg) is inferior to twice-daily dosing (250 mg twice daily) for complicated UTI, showing up to 18.4% difference in bacteriologic eradication rates favoring the divided dose regimen. 3 Always use twice-daily dosing for serious infections.

Pediatric Underdosing

Always calculate pediatric doses based on actual body weight, not age alone, and verify syrup concentration before calculating mL doses to avoid underdosing. 8 The 1 g/day maximum applies regardless of weight in children <45 kg. 1