Ciprofloxacin Dosing
For adults with normal renal function, administer ciprofloxacin 500-750 mg orally every 12 hours or 400 mg intravenously every 8-12 hours, with the specific dose determined by infection severity and pathogen susceptibility. 1
Standard Adult Dosing by Infection Type
Oral dosing:
- Uncomplicated UTI: 250 mg every 12 hours for 3 days 2
- Complicated UTI/Pyelonephritis: 500 mg every 12 hours for 7 days (or 1000 mg extended-release daily) in areas where fluoroquinolone resistance is <10% 3
- Intra-abdominal infections: 500 mg orally every 12 hours combined with metronidazole 4, 3
- Respiratory infections (bronchiectasis): 500-750 mg every 12 hours for 14 days 4
- Severe infections: 750 mg every 12 hours 1
- Inhalational anthrax (post-exposure): 500 mg every 12 hours for 60 days 5, 1
- Meningococcal prophylaxis: 500 mg single dose 3, 6
Intravenous dosing:
- Standard dose: 400 mg every 12 hours 4, 1
- Severe infections or Pseudomonas: 400 mg every 8 hours 4, 1
- Plague: 400 mg every 8 hours 3
Renal Dose Adjustments
Ciprofloxacin is eliminated primarily by renal excretion, requiring dose modification in renal impairment 1:
- CrCl >50 mL/min: Use standard dosing 1
- CrCl 30-50 mL/min: 250-500 mg every 12 hours (oral) or 400 mg every 12 hours (IV) 3, 1
- CrCl 10-30 mL/min: 250-500 mg every 18 hours 3, 6, 1
- CrCl <10 mL/min: 250-500 mg every 18-24 hours 3, 6, 1
- Hemodialysis: 250-500 mg orally or 200-400 mg IV every 24 hours, administered after dialysis 6, 1
Critical pitfall: Giving ciprofloxacin before dialysis leads to subtherapeutic levels; always administer post-dialysis 6.
Dosing for Augmented Renal Clearance
For critically ill patients with eGFR >130 mL/min and infections caused by pathogens with MIC ≥0.5 mg/L, standard dosing is insufficient 7. Higher doses up to 600 mg four times daily or more may be required to achieve adequate target attainment (AUC/MIC >125) 3, 7. A dose of 400 mg every 12 hours is only sufficient for patients with eGFR <130 mL/min and pathogens with MIC ≤0.125 mg/L 7.
Pediatric Dosing
Ciprofloxacin should only be used in children when no acceptable alternative exists due to risk of reversible arthralgia (~3% incidence), and pediatric infectious disease consultation is strongly recommended 5, 6.
FDA-approved pediatric indications:
Dosing regimens:
- Neonates (0-28 days): 7-10 mg/kg IV every 12 hours or 15 mg/kg orally every 12 hours 5, 6
- Children (oral): 10-20 mg/kg every 12 hours (maximum 750 mg per dose) 5, 6, 1
- Children (IV): 10 mg/kg every 8-12 hours (maximum 400 mg per dose) 5, 6, 1
- Complicated UTI/pyelonephritis (IV): 6-10 mg/kg every 8 hours (maximum 400 mg per dose) 1
- Inhalational anthrax: 15 mg/kg orally every 12 hours (maximum 500 mg per dose) for 60 days 5, 1
- Total daily dose: Must not exceed 20-30 mg/kg/day regardless of weight 5, 6
Important caveat: Maximum daily dose is 1 g/day for most indications regardless of weight 5, 1.
Administration Considerations
Avoid co-administration with divalent cations (antacids, calcium, iron, zinc) as they chelate ciprofloxacin and reduce absorption 5, 3. Administer ciprofloxacin at least 2 hours before or 6 hours after these products 5, 3, 6.
Peak serum concentrations occur 1-2 hours after oral dosing, with rapid and complete absorption 6.
Monitoring Requirements
Mandatory monitoring includes:
- ECG: Baseline, at 2 weeks, and after adding any QT-prolonging medication due to risk of QTc prolongation 5, 3, 6
- Blood glucose: Regular monitoring in diabetic patients due to hypoglycemia risk 5, 3, 6
- Renal and hepatic function: Intermittent CBC, serum creatinine, and liver function tests throughout treatment 5, 3, 6
- Therapeutic drug monitoring: Consider for severe infections with poor clinical response; target trough ≈1 mg/L and peak ≈3 mg/L for 500 mg every 12 hours regimen 5, 6
Contraindications and Special Populations
Pregnancy: Use only for life-threatening infections (e.g., inhalational anthrax) when benefits outweigh fetal risks 5, 6.
Breastfeeding: Avoid when alternative agents are available 6.
Pediatric patients <18 years: Avoid unless no acceptable alternative exists 5, 6. Reversible arthralgia occurs in approximately 3% of pediatric patients, but no radiographic evidence of permanent cartilage damage has been demonstrated 5, 6.
Do not use as first-line for:
- Acute otitis media or sinusitis 5
- Community-acquired pneumonia 5
- Routine skin and soft-tissue infections 5
Critical warning: Do not give concurrent antidiarrheal agents (loperamide, diphenoxylate) in infectious diarrhea, especially when Shiga-toxin-producing E. coli is possible, as this markedly increases risk of hemolytic-uremic syndrome 6.
Alternative Therapies When Ciprofloxacin Is Contraindicated
- Uncomplicated UTI: Cephalosporins, trimethoprim-sulfamethoxazole (if susceptible), or ampicillin + gentamicin 6
- Severe gram-negative infections: Ceftazidime, ceftriaxone, meropenem, or imipenem 6
- Pseudomonas infections: Ceftazidime, piperacillin-tazobactam, meropenem, or colistin 4, 6
- Multidrug-resistant organisms: Ceftazidime-avibactam, meropenem-vaborbactam, or colistin based on susceptibility 6
Common Dosing Errors to Avoid
Do not use standard 500 mg every 12 hours dosing in end-stage renal disease without dose reduction—this leads to drug accumulation and toxicity 6. For patients with CrCl <30 mL/min, extend the dosing interval to every 18-24 hours 1.
Do not empirically use fluoroquinolones for pyelonephritis if local resistance exceeds 10%; consider initial parenteral therapy with ceftriaxone or aminoglycoside instead 3.
Avoid empirical fluoroquinolone use for acute cystitis when other UTI antimicrobials can be used, due to collateral damage concerns and the need to preserve these agents for more serious infections 3.